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Re: S/N ; F ratio ; and RC vs LX200

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  • Chris Johnston
    Gents The differences between an SCT and RC are well qualified mathematically and experimentally and are nicely laid out in Rutten and van Venrooij Telescope
    Message 1 of 26 , May 31, 2003
      Gents

      The differences between an SCT and RC are well qualified
      mathematically and experimentally and are nicely laid out in Rutten
      and van Venrooij "Telescope Optics".

      The simple facts are :-

      On axis perfomance between each will be similar assuming the scope is
      collimated.

      The off axis coma of the RC will be superior to the SCT resulting in
      a number of imaging advantages.

      Of course the seeing, sky background and experience will affect the
      result but all things being equal the RC will outperform the SCT off
      axis. Whether this is worth the extra $ will depend on how
      fanatical you are.

      Peter Ward has created an interesting example of the differences on a
      mouse roll over image at

      http://www.atscope.com.au/rcos.html

      You might like to have a look at that.

      Of course there are ways of mitigating the effects of coma, but they
      require adjustment lenses cutting down contrast, and small amounts of
      coma will still be present.

      No question that compared to a quality SCT, assuming you can get one,
      the RC is a real luxury for what may appear to be a small advantage,
      but that seems to be the general rule in regard to many capital items
      where the extra quality escapes the mass production equation. You
      pay significantly more for the extra bit of quality.

      Cheers
      Chris
    • laurenc319
      hi, FYI here s a link to a good article by R.F. Royce http://www.rfroyce.com/cassegrains.htm clear skies, Larry Citro
      Message 2 of 26 , Jun 1, 2003
        hi,

        FYI here's a link to a good article by R.F. Royce


        http://www.rfroyce.com/cassegrains.htm


        clear skies,


        Larry Citro
      • Wodaski Yahoo account
        It has been my experience, both visually and with CCD, that poor optics are more affected by seeing that good optics. An interesting case in point: On a night
        Message 3 of 26 , Jun 1, 2003
          It has been my experience, both visually and with CCD, that poor optics are
          more affected by seeing that good optics.

          An interesting case in point: On a night of exceptional seeing at New Mexico
          Skies, I took an image of M51 with the C14 and ST-10 binned 2x2 that was
          very good. Still a little soft, however. In the first tests of the new 20"
          RC, on a night that was so bad I didn't bother to image with the C14, the
          images of M51 were as good as they were on that best night with the C14 -
          despite the fact that we are still making adjustments to the RC and it's
          mounting to improve performance. This fact just blew me away.

          Ron Wodaski
          author of The New CCD Astronomy
          http://www.newastro.com


          -----Original Message-----
          From: clearviewh [mailto:clearview@...]
          Sent: Saturday, May 31, 2003 8:13 PM
          To: ccd-newastro@yahoogroups.com
          Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200


          To tell you the truth, I think a LOT of it is location. Sometimes I
          whine about not having the money for a nice RC and Paramount mount
          but I have spent plenty on the domed observatory. Thing is, I wonder
          if I would get full value out of that kind of setup here. When seeing
          is good, which is not that often, I get images that I am very proud
          of. The rest of the time, as I watch the guide star jumping around
          from poor seeing, I wonder just how well even a Paramount would
          perform here.....at least that's what I keep telling myself.... LOL
          Ed

          --- In ccd-newastro@yahoogroups.com, "Mark de Regt" <deregt@e...>
          wrote:
          > Ed,
          >
          > This is something I have thought a lot about, and talked with
          people with
          > experience with both SCTs and RCs. I believe, of course, that the
          RC optics
          > are better than my LX200, but I also believet that my LX200 has
          excellent
          > optics. When you talk about the RC images you see, it is worth
          keeping in
          > mind that people with RCs tend to be experienced imagers, and often
          have
          > superior locations. Taking nothing away from Adam Block at Kitt
          Peak (whose
          > images have become routinely sublime, they are so wonderful), and
          others, it
          > is also worth remembering that their scopes are bigger than most of
          ours.
          > Most of the RCs you see are 12.5 inch, with some at 14.5 inch, 16
          inch, and
          > Adam now uses a 20 inch. I know that emulsion photographers say
          that focal
          > ratio is the sole determiner of exposure length, but, with CCD
          imaging of
          > the heavens, I don't believe it--The larger the aperture, the less
          time it
          > takes to get good S/N, I think. Add to that the superior location
          someone
          > like Adam has--no light pollution and 7000 foot elevation, and you
          can't
          > even compare that circumstance to what most of us deal with. Add
          to that
          > the fact the many of the best imagers manage to get several images
          a month
          > (at least), year round, while I'm happy if I get ten in a year; the
          > experience in image acquisition and image processing, and its
          contribution
          > to the final result, should not be underestimated,
          >
          > I think that the optics themselves plays a pretty minor role in
          what you see
          > with exposure length; the steadier mount is more important, but the
          AO-7
          > makes up for most of that. I believe that dark skies, elevation,
          and larger
          > aperture has a lot more to do with it than RC quality.
          >
          >
          >
          > > -----Original Message-----
          > > From: clearviewh [mailto:clearview@c...]
          > > Sent: Saturday, May 31, 2003 6:00 PM
          > > To: ccd-newastro@yahoogroups.com
          > > Subject: [ccd-newastro] S/N ; F ratio ; and RC vs LX200
          > >
          > >
          > > Just wanted to take this opportunity, while Ron is apparently
          gone,
          > > to comment on the question of S/N only being related to F.R. I
          have
          > > known for a long time, that with my LX200, I have to take MUCH
          longer
          > > exposure times than someone with say an RC on a Paramount with the
          > > same FL and diameter. I have gone round and round on the subject
          and
          > > finally deceided that the QUALITY of the setup ALSO plays a role
          in
          > > S/N. Perhaps not, I agree, in the ACTUAL S/N, but a better setup
          > > spreads the signal around less, giving a better image. I have to
          take
          > > a much longer exposures cause the poorer tracking, and optics, of
          my
          > > LX200, spreads my signal out more..... bloated stars.....etc. So
          > > when say a Rob Gendler with his 12 in RC at F9 takes a L:R:G:B of
          > > 120:40:60:60, I have to take a 180:60:90:90 to get an image that
          > > appears to have a similar S/N even at F5....Comments??
          > > Ed
          > >
          > >
          > >
          > > To unsubscribe from this group, send an email to:
          > > ccd-newastro-unsubscribe@egroups.com
          > >
          > >
          > >
          > > Your use of Yahoo! Groups is subject to
          http://docs.yahoo.com/info/terms/
          > >
          > >



          To unsubscribe from this group, send an email to:
          ccd-newastro-unsubscribe@egroups.com



          Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
        • Randy Nulman
          I saw the same thing when I got my 12.5 RC. The optics of my old C11 were relatively good, but my fwhm improved by almost 25% with the RC! (This was comparing
          Message 4 of 26 , Jun 1, 2003
            I saw the same thing when I got my 12.5 RC. The optics of my old C11
            were relatively good, but my fwhm improved by almost 25% with the RC!
            (This was comparing "on axis" stars for both scopes)

            I was originally expecting only an "off axis" improvement, but the
            quality of the optics in the RCOS really made a difference.

            Randy Nulman

            --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
            <yahoo@w...> wrote:
            > It has been my experience, both visually and with CCD, that poor
            optics are
            > more affected by seeing that good optics.
            >
            > An interesting case in point: On a night of exceptional seeing at
            New Mexico
            > Skies, I took an image of M51 with the C14 and ST-10 binned 2x2
            that was
            > very good. Still a little soft, however. In the first tests of the
            new 20"
            > RC, on a night that was so bad I didn't bother to image with the
            C14, the
            > images of M51 were as good as they were on that best night with the
            C14 -
            > despite the fact that we are still making adjustments to the RC and
            it's
            > mounting to improve performance. This fact just blew me away.
            >
            > Ron Wodaski
            > author of The New CCD Astronomy
            > http://www.newastro.com
            >
            >
            > -----Original Message-----
            > From: clearviewh [mailto:clearview@c...]
            > Sent: Saturday, May 31, 2003 8:13 PM
            > To: ccd-newastro@yahoogroups.com
            > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
            >
            >
            > To tell you the truth, I think a LOT of it is location. Sometimes I
            > whine about not having the money for a nice RC and Paramount mount
            > but I have spent plenty on the domed observatory. Thing is, I wonder
            > if I would get full value out of that kind of setup here. When
            seeing
            > is good, which is not that often, I get images that I am very proud
            > of. The rest of the time, as I watch the guide star jumping around
            > from poor seeing, I wonder just how well even a Paramount would
            > perform here.....at least that's what I keep telling myself.... LOL
            > Ed
            >
            > --- In ccd-newastro@yahoogroups.com, "Mark de Regt" <deregt@e...>
            > wrote:
            > > Ed,
            > >
            > > This is something I have thought a lot about, and talked with
            > people with
            > > experience with both SCTs and RCs. I believe, of course, that the
            > RC optics
            > > are better than my LX200, but I also believet that my LX200 has
            > excellent
            > > optics. When you talk about the RC images you see, it is worth
            > keeping in
            > > mind that people with RCs tend to be experienced imagers, and
            often
            > have
            > > superior locations. Taking nothing away from Adam Block at Kitt
            > Peak (whose
            > > images have become routinely sublime, they are so wonderful), and
            > others, it
            > > is also worth remembering that their scopes are bigger than most
            of
            > ours.
            > > Most of the RCs you see are 12.5 inch, with some at 14.5 inch, 16
            > inch, and
            > > Adam now uses a 20 inch. I know that emulsion photographers say
            > that focal
            > > ratio is the sole determiner of exposure length, but, with CCD
            > imaging of
            > > the heavens, I don't believe it--The larger the aperture, the less
            > time it
            > > takes to get good S/N, I think. Add to that the superior location
            > someone
            > > like Adam has--no light pollution and 7000 foot elevation, and you
            > can't
            > > even compare that circumstance to what most of us deal with. Add
            > to that
            > > the fact the many of the best imagers manage to get several images
            > a month
            > > (at least), year round, while I'm happy if I get ten in a year;
            the
            > > experience in image acquisition and image processing, and its
            > contribution
            > > to the final result, should not be underestimated,
            > >
            > > I think that the optics themselves plays a pretty minor role in
            > what you see
            > > with exposure length; the steadier mount is more important, but
            the
            > AO-7
            > > makes up for most of that. I believe that dark skies, elevation,
            > and larger
            > > aperture has a lot more to do with it than RC quality.
            > >
            > >
            > >
            > > > -----Original Message-----
            > > > From: clearviewh [mailto:clearview@c...]
            > > > Sent: Saturday, May 31, 2003 6:00 PM
            > > > To: ccd-newastro@yahoogroups.com
            > > > Subject: [ccd-newastro] S/N ; F ratio ; and RC vs LX200
            > > >
            > > >
            > > > Just wanted to take this opportunity, while Ron is apparently
            > gone,
            > > > to comment on the question of S/N only being related to F.R. I
            > have
            > > > known for a long time, that with my LX200, I have to take MUCH
            > longer
            > > > exposure times than someone with say an RC on a Paramount with
            the
            > > > same FL and diameter. I have gone round and round on the subject
            > and
            > > > finally deceided that the QUALITY of the setup ALSO plays a role
            > in
            > > > S/N. Perhaps not, I agree, in the ACTUAL S/N, but a better setup
            > > > spreads the signal around less, giving a better image. I have to
            > take
            > > > a much longer exposures cause the poorer tracking, and optics,
            of
            > my
            > > > LX200, spreads my signal out more..... bloated stars.....etc.
            So
            > > > when say a Rob Gendler with his 12 in RC at F9 takes a L:R:G:B
            of
            > > > 120:40:60:60, I have to take a 180:60:90:90 to get an image that
            > > > appears to have a similar S/N even at F5....Comments??
            > > > Ed
            > > >
            > > >
            > > >
            > > > To unsubscribe from this group, send an email to:
            > > > ccd-newastro-unsubscribe@egroups.com
            > > >
            > > >
            > > >
            > > > Your use of Yahoo! Groups is subject to
            > http://docs.yahoo.com/info/terms/
            > > >
            > > >
            >
            >
            >
            > To unsubscribe from this group, send an email to:
            > ccd-newastro-unsubscribe@egroups.com
            >
            >
            >
            > Your use of Yahoo! Groups is subject to
            http://docs.yahoo.com/info/terms/
          • Steve Leikind
            Randy, What you say may well be true, but there are a lot of variables here and it s difficult to separate the wheat from the chaff . Your SCT undoubtedly
            Message 5 of 26 , Jun 1, 2003
              Randy,

              What you say may well be true, but there are a lot of variables here
              and it's difficult to separate "the wheat from the chaff". Your SCT
              undoubtedly didn't have the same kind of optical quality that your
              Ritchey does. Yet Ed Grafton, Thierry Legault, and Damian Peach have
              taken some extraordinarily good images of Jupiter and Saturn with
              their SCT's and I am not sure that I have seen any with Ritchey's
              that are better even though, for a given aperture, they cost five
              times to ten times more. Some people claim that those guys were
              simply lucky to get good SCT's with outstanding optics. Then I've
              also heard people say that the quality on some of the newer SCT's is
              generally quite good.

              Another variable is collimation. It sounds like Legault collimates
              his 12" every night and often multiple times a night. He has a
              lengthy discussion about collimation and the effects of
              miscollimation on his web site and he underlines his main point
              that "No high resolution result can be hoped without a irreproachable
              collimation". I wonder how many SCT imagers have collimation that
              isn't simply good, but "irreproachable"? Every time an SCT
              mirror "flops" a little, collimation changes with these scopes. I
              suppose that no wanting to constantly recollimate your scope may
              justify the cost differential between Ritchey's and SCT's for many.

              If it's true that there are big differences in the quality of SCT's
              being produced now, perhaps it makes sense to buy one new from a
              retailer who accepts returns if you are not satisfied. Then you keep
              returning them until you find one with superior quality. If you have
              the patience for this, perhaps you would be rewarded by getting a
              scope that's as good as a Ritchey (on-axis) at 10% of the cost???

              It's also possible that people like Legault and Grafton are so much
              better at taking and processing planetary images that they maximize
              the potential of their scopes, while people with superior optics have
              not managed to do that. It would be nice to get the whole story on
              this, but I am not sure we ever will.

              Steve

              --- In ccd-newastro@yahoogroups.com, "Randy Nulman" <rj.nulman@v...>
              wrote:
              > I saw the same thing when I got my 12.5 RC. The optics of my old
              C11
              > were relatively good, but my fwhm improved by almost 25% with the
              RC!
              > (This was comparing "on axis" stars for both scopes)
              >
              > I was originally expecting only an "off axis" improvement, but the
              > quality of the optics in the RCOS really made a difference.
              >
              > Randy Nulman
              >
              > --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
              > <yahoo@w...> wrote:
              > > It has been my experience, both visually and with CCD, that poor
              > optics are
              > > more affected by seeing that good optics.
              > >
              > > An interesting case in point: On a night of exceptional seeing at
              > New Mexico
              > > Skies, I took an image of M51 with the C14 and ST-10 binned 2x2
              > that was
              > > very good. Still a little soft, however. In the first tests of
              the
              > new 20"
              > > RC, on a night that was so bad I didn't bother to image with the
              > C14, the
              > > images of M51 were as good as they were on that best night with
              the
              > C14 -
              > > despite the fact that we are still making adjustments to the RC
              and
              > it's
              > > mounting to improve performance. This fact just blew me away.
              > >
              > > Ron Wodaski
              > > author of The New CCD Astronomy
              > > http://www.newastro.com
              > >
              > >
              > > -----Original Message-----
              > > From: clearviewh [mailto:clearview@c...]
              > > Sent: Saturday, May 31, 2003 8:13 PM
              > > To: ccd-newastro@yahoogroups.com
              > > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
              > >
              > >
              > > To tell you the truth, I think a LOT of it is location. Sometimes
              I
              > > whine about not having the money for a nice RC and Paramount mount
              > > but I have spent plenty on the domed observatory. Thing is, I
              wonder
              > > if I would get full value out of that kind of setup here. When
              > seeing
              > > is good, which is not that often, I get images that I am very
              proud
              > > of. The rest of the time, as I watch the guide star jumping around
              > > from poor seeing, I wonder just how well even a Paramount would
              > > perform here.....at least that's what I keep telling myself....
              LOL
              > > Ed
              > >
              > > --- In ccd-newastro@yahoogroups.com, "Mark de Regt" <deregt@e...>
              > > wrote:
              > > > Ed,
              > > >
              > > > This is something I have thought a lot about, and talked with
              > > people with
              > > > experience with both SCTs and RCs. I believe, of course, that
              the
              > > RC optics
              > > > are better than my LX200, but I also believet that my LX200 has
              > > excellent
              > > > optics. When you talk about the RC images you see, it is worth
              > > keeping in
              > > > mind that people with RCs tend to be experienced imagers, and
              > often
              > > have
              > > > superior locations. Taking nothing away from Adam Block at Kitt
              > > Peak (whose
              > > > images have become routinely sublime, they are so wonderful),
              and
              > > others, it
              > > > is also worth remembering that their scopes are bigger than
              most
              > of
              > > ours.
              > > > Most of the RCs you see are 12.5 inch, with some at 14.5 inch,
              16
              > > inch, and
              > > > Adam now uses a 20 inch. I know that emulsion photographers say
              > > that focal
              > > > ratio is the sole determiner of exposure length, but, with CCD
              > > imaging of
              > > > the heavens, I don't believe it--The larger the aperture, the
              less
              > > time it
              > > > takes to get good S/N, I think. Add to that the superior
              location
              > > someone
              > > > like Adam has--no light pollution and 7000 foot elevation, and
              you
              > > can't
              > > > even compare that circumstance to what most of us deal with.
              Add
              > > to that
              > > > the fact the many of the best imagers manage to get several
              images
              > > a month
              > > > (at least), year round, while I'm happy if I get ten in a year;
              > the
              > > > experience in image acquisition and image processing, and its
              > > contribution
              > > > to the final result, should not be underestimated,
              > > >
              > > > I think that the optics themselves plays a pretty minor role in
              > > what you see
              > > > with exposure length; the steadier mount is more important, but
              > the
              > > AO-7
              > > > makes up for most of that. I believe that dark skies,
              elevation,
              > > and larger
              > > > aperture has a lot more to do with it than RC quality.
              > > >
              > > >
              > > >
              > > > > -----Original Message-----
              > > > > From: clearviewh [mailto:clearview@c...]
              > > > > Sent: Saturday, May 31, 2003 6:00 PM
              > > > > To: ccd-newastro@yahoogroups.com
              > > > > Subject: [ccd-newastro] S/N ; F ratio ; and RC vs LX200
              > > > >
              > > > >
              > > > > Just wanted to take this opportunity, while Ron is apparently
              > > gone,
              > > > > to comment on the question of S/N only being related to F.R.
              I
              > > have
              > > > > known for a long time, that with my LX200, I have to take MUCH
              > > longer
              > > > > exposure times than someone with say an RC on a Paramount
              with
              > the
              > > > > same FL and diameter. I have gone round and round on the
              subject
              > > and
              > > > > finally deceided that the QUALITY of the setup ALSO plays a
              role
              > > in
              > > > > S/N. Perhaps not, I agree, in the ACTUAL S/N, but a better
              setup
              > > > > spreads the signal around less, giving a better image. I have
              to
              > > take
              > > > > a much longer exposures cause the poorer tracking, and
              optics,
              > of
              > > my
              > > > > LX200, spreads my signal out more..... bloated
              stars.....etc.
              > So
              > > > > when say a Rob Gendler with his 12 in RC at F9 takes a
              L:R:G:B
              > of
              > > > > 120:40:60:60, I have to take a 180:60:90:90 to get an image
              that
              > > > > appears to have a similar S/N even at F5....Comments??
              > > > > Ed
              > > > >
              > > > >
              > > > >
              > > > > To unsubscribe from this group, send an email to:
              > > > > ccd-newastro-unsubscribe@egroups.com
              > > > >
              > > > >
              > > > >
              > > > > Your use of Yahoo! Groups is subject to
              > > http://docs.yahoo.com/info/terms/
              > > > >
              > > > >
              > >
              > >
              > >
              > > To unsubscribe from this group, send an email to:
              > > ccd-newastro-unsubscribe@egroups.com
              > >
              > >
              > >
              > > Your use of Yahoo! Groups is subject to
              > http://docs.yahoo.com/info/terms/
            • clearviewh
              I think that it only makes sense to think that superior optics will perform better under all conditions than pooer optics, and this includes bad seeing.
              Message 6 of 26 , Jun 1, 2003
                I think that it only makes sense to think that superior optics will
                perform better under all conditions than pooer optics, and this
                includes bad seeing. However, to make use of the superior optics, one
                must also have a superior mount and the whole thing just get's a
                little pricey to say the least. Also, those "better optics,
                performing better than the others even during poor seeing still can't
                match the quality that they would get in excellent seeing, and it's
                only THOSE kind of images, in my opinion, that make the price worth
                wild After all, if I have to spend 10 trimes as much for a setup, I
                would want 10 times the quality in the images, and I'm not sure I
                would get that in my poor seeing
                I think it is safe to say that most of have the setup that "works"
                for us, or we change it. For me, the best optics and mount in the
                world would'nt mean a hill of beans if I had to carry it out to the
                end of my street, climb a ladder to cover a street light and then sit
                there with the bugs to image. I need my heated and air conditioned
                control room, lazy boy, and the ability to image in an hours notice
                and shut down in 15 min to make it worth wild, and I can'yt afford
                this and the best scope...although I DO wish I could <g>
                Ed

                --- In ccd-newastro@yahoogroups.com, "Steve Leikind" <sleikind@v...>
                wrote:
                > Randy,
                >
                > What you say may well be true, but there are a lot of variables
                here
                > and it's difficult to separate "the wheat from the chaff". Your SCT
                > undoubtedly didn't have the same kind of optical quality that your
                > Ritchey does. Yet Ed Grafton, Thierry Legault, and Damian Peach
                have
                > taken some extraordinarily good images of Jupiter and Saturn with
                > their SCT's and I am not sure that I have seen any with Ritchey's
                > that are better even though, for a given aperture, they cost five
                > times to ten times more. Some people claim that those guys were
                > simply lucky to get good SCT's with outstanding optics. Then I've
                > also heard people say that the quality on some of the newer SCT's
                is
                > generally quite good.
                >
                > Another variable is collimation. It sounds like Legault collimates
                > his 12" every night and often multiple times a night. He has a
                > lengthy discussion about collimation and the effects of
                > miscollimation on his web site and he underlines his main point
                > that "No high resolution result can be hoped without a
                irreproachable
                > collimation". I wonder how many SCT imagers have collimation that
                > isn't simply good, but "irreproachable"? Every time an SCT
                > mirror "flops" a little, collimation changes with these scopes. I
                > suppose that no wanting to constantly recollimate your scope may
                > justify the cost differential between Ritchey's and SCT's for many.
                >
                > If it's true that there are big differences in the quality of SCT's
                > being produced now, perhaps it makes sense to buy one new from a
                > retailer who accepts returns if you are not satisfied. Then you
                keep
                > returning them until you find one with superior quality. If you
                have
                > the patience for this, perhaps you would be rewarded by getting a
                > scope that's as good as a Ritchey (on-axis) at 10% of the cost???
                >
                > It's also possible that people like Legault and Grafton are so much
                > better at taking and processing planetary images that they maximize
                > the potential of their scopes, while people with superior optics
                have
                > not managed to do that. It would be nice to get the whole story on
                > this, but I am not sure we ever will.
                >
                > Steve
                >
                > --- In ccd-newastro@yahoogroups.com, "Randy Nulman"
                <rj.nulman@v...>
                > wrote:
                > > I saw the same thing when I got my 12.5 RC. The optics of my old
                > C11
                > > were relatively good, but my fwhm improved by almost 25% with the
                > RC!
                > > (This was comparing "on axis" stars for both scopes)
                > >
                > > I was originally expecting only an "off axis" improvement, but
                the
                > > quality of the optics in the RCOS really made a difference.
                > >
                > > Randy Nulman
                > >
                > > --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
                > > <yahoo@w...> wrote:
                > > > It has been my experience, both visually and with CCD, that
                poor
                > > optics are
                > > > more affected by seeing that good optics.
                > > >
                > > > An interesting case in point: On a night of exceptional seeing
                at
                > > New Mexico
                > > > Skies, I took an image of M51 with the C14 and ST-10 binned 2x2
                > > that was
                > > > very good. Still a little soft, however. In the first tests of
                > the
                > > new 20"
                > > > RC, on a night that was so bad I didn't bother to image with
                the
                > > C14, the
                > > > images of M51 were as good as they were on that best night with
                > the
                > > C14 -
                > > > despite the fact that we are still making adjustments to the RC
                > and
                > > it's
                > > > mounting to improve performance. This fact just blew me away.
                > > >
                > > > Ron Wodaski
                > > > author of The New CCD Astronomy
                > > > http://www.newastro.com
                > > >
                > > >
                > > > -----Original Message-----
                > > > From: clearviewh [mailto:clearview@c...]
                > > > Sent: Saturday, May 31, 2003 8:13 PM
                > > > To: ccd-newastro@yahoogroups.com
                > > > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
                > > >
                > > >
                > > > To tell you the truth, I think a LOT of it is location.
                Sometimes
                > I
                > > > whine about not having the money for a nice RC and Paramount
                mount
                > > > but I have spent plenty on the domed observatory. Thing is, I
                > wonder
                > > > if I would get full value out of that kind of setup here. When
                > > seeing
                > > > is good, which is not that often, I get images that I am very
                > proud
                > > > of. The rest of the time, as I watch the guide star jumping
                around
                > > > from poor seeing, I wonder just how well even a Paramount would
                > > > perform here.....at least that's what I keep telling
                myself....
                > LOL
                > > > Ed
                > > >
                > > > --- In ccd-newastro@yahoogroups.com, "Mark de Regt"
                <deregt@e...>
                > > > wrote:
                > > > > Ed,
                > > > >
                > > > > This is something I have thought a lot about, and talked with
                > > > people with
                > > > > experience with both SCTs and RCs. I believe, of course,
                that
                > the
                > > > RC optics
                > > > > are better than my LX200, but I also believet that my LX200
                has
                > > > excellent
                > > > > optics. When you talk about the RC images you see, it is
                worth
                > > > keeping in
                > > > > mind that people with RCs tend to be experienced imagers, and
                > > often
                > > > have
                > > > > superior locations. Taking nothing away from Adam Block at
                Kitt
                > > > Peak (whose
                > > > > images have become routinely sublime, they are so wonderful),
                > and
                > > > others, it
                > > > > is also worth remembering that their scopes are bigger than
                > most
                > > of
                > > > ours.
                > > > > Most of the RCs you see are 12.5 inch, with some at 14.5
                inch,
                > 16
                > > > inch, and
                > > > > Adam now uses a 20 inch. I know that emulsion photographers
                say
                > > > that focal
                > > > > ratio is the sole determiner of exposure length, but, with CCD
                > > > imaging of
                > > > > the heavens, I don't believe it--The larger the aperture, the
                > less
                > > > time it
                > > > > takes to get good S/N, I think. Add to that the superior
                > location
                > > > someone
                > > > > like Adam has--no light pollution and 7000 foot elevation,
                and
                > you
                > > > can't
                > > > > even compare that circumstance to what most of us deal with.
                > Add
                > > > to that
                > > > > the fact the many of the best imagers manage to get several
                > images
                > > > a month
                > > > > (at least), year round, while I'm happy if I get ten in a
                year;
                > > the
                > > > > experience in image acquisition and image processing, and its
                > > > contribution
                > > > > to the final result, should not be underestimated,
                > > > >
                > > > > I think that the optics themselves plays a pretty minor role
                in
                > > > what you see
                > > > > with exposure length; the steadier mount is more important,
                but
                > > the
                > > > AO-7
                > > > > makes up for most of that. I believe that dark skies,
                > elevation,
                > > > and larger
                > > > > aperture has a lot more to do with it than RC quality.
                > > > >
                > > > >
                > > > >
                > > > > > -----Original Message-----
                > > > > > From: clearviewh [mailto:clearview@c...]
                > > > > > Sent: Saturday, May 31, 2003 6:00 PM
                > > > > > To: ccd-newastro@yahoogroups.com
                > > > > > Subject: [ccd-newastro] S/N ; F ratio ; and RC vs LX200
                > > > > >
                > > > > >
                > > > > > Just wanted to take this opportunity, while Ron is
                apparently
                > > > gone,
                > > > > > to comment on the question of S/N only being related to
                F.R.
                > I
                > > > have
                > > > > > known for a long time, that with my LX200, I have to take
                MUCH
                > > > longer
                > > > > > exposure times than someone with say an RC on a Paramount
                > with
                > > the
                > > > > > same FL and diameter. I have gone round and round on the
                > subject
                > > > and
                > > > > > finally deceided that the QUALITY of the setup ALSO plays a
                > role
                > > > in
                > > > > > S/N. Perhaps not, I agree, in the ACTUAL S/N, but a better
                > setup
                > > > > > spreads the signal around less, giving a better image. I
                have
                > to
                > > > take
                > > > > > a much longer exposures cause the poorer tracking, and
                > optics,
                > > of
                > > > my
                > > > > > LX200, spreads my signal out more..... bloated
                > stars.....etc.
                > > So
                > > > > > when say a Rob Gendler with his 12 in RC at F9 takes a
                > L:R:G:B
                > > of
                > > > > > 120:40:60:60, I have to take a 180:60:90:90 to get an image
                > that
                > > > > > appears to have a similar S/N even at F5....Comments??
                > > > > > Ed
                > > > > >
                > > > > >
                > > > > >
                > > > > > To unsubscribe from this group, send an email to:
                > > > > > ccd-newastro-unsubscribe@egroups.com
                > > > > >
                > > > > >
                > > > > >
                > > > > > Your use of Yahoo! Groups is subject to
                > > > http://docs.yahoo.com/info/terms/
                > > > > >
                > > > > >
                > > >
                > > >
                > > >
                > > > To unsubscribe from this group, send an email to:
                > > > ccd-newastro-unsubscribe@egroups.com
                > > >
                > > >
                > > >
                > > > Your use of Yahoo! Groups is subject to
                > > http://docs.yahoo.com/info/terms/
              • clearviewh
                I don t belive in luck when it comes to this stuff. These guys would have been producing great images no matter what. When dealing with SCTs and in particular
                Message 7 of 26 , Jun 1, 2003
                  I don't belive in luck when it comes to this stuff. These guys would
                  have been producing great images no matter what. When dealing with
                  SCTs and in particular LX200s one NEEDS to pay close attention to all
                  the little details and reduce all the little inconsistencies down to
                  a minimum, one at a time till the system operates at it's optimum.
                  That's what I do. I check my polar alignment regularly cause flexure
                  causes it to change. I check and adjust my collomnation quite a bit.
                  I check and adjust my guiding rate cause my LX200 is not consistant,
                  I always cool to the max., I keep the setup balanced cause then the
                  guide corections seem to be smoother, I take lots of darks, always
                  use flats, I use all the latest combines like Sigma if I learn to
                  understand them..etc., etc., etc. It ain't luck... I think with the
                  superior optics and mounts, one can afford to be a little lazier with
                  these things and still produce good images, but not an LX200
                  Ed

                  --- In ccd-newastro@yahoogroups.com, "Steve Leikind" <sleikind@v...>
                  wrote:
                  > Randy,
                  >
                  > What you say may well be true, but there are a lot of variables
                  here
                  > and it's difficult to separate "the wheat from the chaff". Your SCT
                  > undoubtedly didn't have the same kind of optical quality that your
                  > Ritchey does. Yet Ed Grafton, Thierry Legault, and Damian Peach
                  have
                  > taken some extraordinarily good images of Jupiter and Saturn with
                  > their SCT's and I am not sure that I have seen any with Ritchey's
                  > that are better even though, for a given aperture, they cost five
                  > times to ten times more. Some people claim that those guys were
                  > simply lucky to get good SCT's with outstanding optics. Then I've
                  > also heard people say that the quality on some of the newer SCT's
                  is
                  > generally quite good.
                  >
                  > Another variable is collimation. It sounds like Legault collimates
                  > his 12" every night and often multiple times a night. He has a
                  > lengthy discussion about collimation and the effects of
                  > miscollimation on his web site and he underlines his main point
                  > that "No high resolution result can be hoped without a
                  irreproachable
                  > collimation". I wonder how many SCT imagers have collimation that
                  > isn't simply good, but "irreproachable"? Every time an SCT
                  > mirror "flops" a little, collimation changes with these scopes. I
                  > suppose that no wanting to constantly recollimate your scope may
                  > justify the cost differential between Ritchey's and SCT's for many.
                  >
                  > If it's true that there are big differences in the quality of SCT's
                  > being produced now, perhaps it makes sense to buy one new from a
                  > retailer who accepts returns if you are not satisfied. Then you
                  keep
                  > returning them until you find one with superior quality. If you
                  have
                  > the patience for this, perhaps you would be rewarded by getting a
                  > scope that's as good as a Ritchey (on-axis) at 10% of the cost???
                  >
                  > It's also possible that people like Legault and Grafton are so much
                  > better at taking and processing planetary images that they maximize
                  > the potential of their scopes, while people with superior optics
                  have
                  > not managed to do that. It would be nice to get the whole story on
                  > this, but I am not sure we ever will.
                  >
                  > Steve
                  >
                  > --- In ccd-newastro@yahoogroups.com, "Randy Nulman"
                  <rj.nulman@v...>
                  > wrote:
                  > > I saw the same thing when I got my 12.5 RC. The optics of my old
                  > C11
                  > > were relatively good, but my fwhm improved by almost 25% with the
                  > RC!
                  > > (This was comparing "on axis" stars for both scopes)
                  > >
                  > > I was originally expecting only an "off axis" improvement, but
                  the
                  > > quality of the optics in the RCOS really made a difference.
                  > >
                  > > Randy Nulman
                  > >
                  > > --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
                  > > <yahoo@w...> wrote:
                  > > > It has been my experience, both visually and with CCD, that
                  poor
                  > > optics are
                  > > > more affected by seeing that good optics.
                  > > >
                  > > > An interesting case in point: On a night of exceptional seeing
                  at
                  > > New Mexico
                  > > > Skies, I took an image of M51 with the C14 and ST-10 binned 2x2
                  > > that was
                  > > > very good. Still a little soft, however. In the first tests of
                  > the
                  > > new 20"
                  > > > RC, on a night that was so bad I didn't bother to image with
                  the
                  > > C14, the
                  > > > images of M51 were as good as they were on that best night with
                  > the
                  > > C14 -
                  > > > despite the fact that we are still making adjustments to the RC
                  > and
                  > > it's
                  > > > mounting to improve performance. This fact just blew me away.
                  > > >
                  > > > Ron Wodaski
                  > > > author of The New CCD Astronomy
                  > > > http://www.newastro.com
                  > > >
                  > > >
                  > > > -----Original Message-----
                  > > > From: clearviewh [mailto:clearview@c...]
                  > > > Sent: Saturday, May 31, 2003 8:13 PM
                  > > > To: ccd-newastro@yahoogroups.com
                  > > > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
                  > > >
                  > > >
                  > > > To tell you the truth, I think a LOT of it is location.
                  Sometimes
                  > I
                  > > > whine about not having the money for a nice RC and Paramount
                  mount
                  > > > but I have spent plenty on the domed observatory. Thing is, I
                  > wonder
                  > > > if I would get full value out of that kind of setup here. When
                  > > seeing
                  > > > is good, which is not that often, I get images that I am very
                  > proud
                  > > > of. The rest of the time, as I watch the guide star jumping
                  around
                  > > > from poor seeing, I wonder just how well even a Paramount would
                  > > > perform here.....at least that's what I keep telling
                  myself....
                  > LOL
                  > > > Ed
                  > > >
                  > > > --- In ccd-newastro@yahoogroups.com, "Mark de Regt"
                  <deregt@e...>
                  > > > wrote:
                  > > > > Ed,
                  > > > >
                  > > > > This is something I have thought a lot about, and talked with
                  > > > people with
                  > > > > experience with both SCTs and RCs. I believe, of course,
                  that
                  > the
                  > > > RC optics
                  > > > > are better than my LX200, but I also believet that my LX200
                  has
                  > > > excellent
                  > > > > optics. When you talk about the RC images you see, it is
                  worth
                  > > > keeping in
                  > > > > mind that people with RCs tend to be experienced imagers, and
                  > > often
                  > > > have
                  > > > > superior locations. Taking nothing away from Adam Block at
                  Kitt
                  > > > Peak (whose
                  > > > > images have become routinely sublime, they are so wonderful),
                  > and
                  > > > others, it
                  > > > > is also worth remembering that their scopes are bigger than
                  > most
                  > > of
                  > > > ours.
                  > > > > Most of the RCs you see are 12.5 inch, with some at 14.5
                  inch,
                  > 16
                  > > > inch, and
                  > > > > Adam now uses a 20 inch. I know that emulsion photographers
                  say
                  > > > that focal
                  > > > > ratio is the sole determiner of exposure length, but, with CCD
                  > > > imaging of
                  > > > > the heavens, I don't believe it--The larger the aperture, the
                  > less
                  > > > time it
                  > > > > takes to get good S/N, I think. Add to that the superior
                  > location
                  > > > someone
                  > > > > like Adam has--no light pollution and 7000 foot elevation,
                  and
                  > you
                  > > > can't
                  > > > > even compare that circumstance to what most of us deal with.
                  > Add
                  > > > to that
                  > > > > the fact the many of the best imagers manage to get several
                  > images
                  > > > a month
                  > > > > (at least), year round, while I'm happy if I get ten in a
                  year;
                  > > the
                  > > > > experience in image acquisition and image processing, and its
                  > > > contribution
                  > > > > to the final result, should not be underestimated,
                  > > > >
                  > > > > I think that the optics themselves plays a pretty minor role
                  in
                  > > > what you see
                  > > > > with exposure length; the steadier mount is more important,
                  but
                  > > the
                  > > > AO-7
                  > > > > makes up for most of that. I believe that dark skies,
                  > elevation,
                  > > > and larger
                  > > > > aperture has a lot more to do with it than RC quality.
                  > > > >
                  > > > >
                  > > > >
                  > > > > > -----Original Message-----
                  > > > > > From: clearviewh [mailto:clearview@c...]
                  > > > > > Sent: Saturday, May 31, 2003 6:00 PM
                  > > > > > To: ccd-newastro@yahoogroups.com
                  > > > > > Subject: [ccd-newastro] S/N ; F ratio ; and RC vs LX200
                  > > > > >
                  > > > > >
                  > > > > > Just wanted to take this opportunity, while Ron is
                  apparently
                  > > > gone,
                  > > > > > to comment on the question of S/N only being related to
                  F.R.
                  > I
                  > > > have
                  > > > > > known for a long time, that with my LX200, I have to take
                  MUCH
                  > > > longer
                  > > > > > exposure times than someone with say an RC on a Paramount
                  > with
                  > > the
                  > > > > > same FL and diameter. I have gone round and round on the
                  > subject
                  > > > and
                  > > > > > finally deceided that the QUALITY of the setup ALSO plays a
                  > role
                  > > > in
                  > > > > > S/N. Perhaps not, I agree, in the ACTUAL S/N, but a better
                  > setup
                  > > > > > spreads the signal around less, giving a better image. I
                  have
                  > to
                  > > > take
                  > > > > > a much longer exposures cause the poorer tracking, and
                  > optics,
                  > > of
                  > > > my
                  > > > > > LX200, spreads my signal out more..... bloated
                  > stars.....etc.
                  > > So
                  > > > > > when say a Rob Gendler with his 12 in RC at F9 takes a
                  > L:R:G:B
                  > > of
                  > > > > > 120:40:60:60, I have to take a 180:60:90:90 to get an image
                  > that
                  > > > > > appears to have a similar S/N even at F5....Comments??
                  > > > > > Ed
                  > > > > >
                  > > > > >
                  > > > > >
                  > > > > > To unsubscribe from this group, send an email to:
                  > > > > > ccd-newastro-unsubscribe@egroups.com
                  > > > > >
                  > > > > >
                  > > > > >
                  > > > > > Your use of Yahoo! Groups is subject to
                  > > > http://docs.yahoo.com/info/terms/
                  > > > > >
                  > > > > >
                  > > >
                  > > >
                  > > >
                  > > > To unsubscribe from this group, send an email to:
                  > > > ccd-newastro-unsubscribe@egroups.com
                  > > >
                  > > >
                  > > >
                  > > > Your use of Yahoo! Groups is subject to
                  > > http://docs.yahoo.com/info/terms/
                • Wodaski Yahoo account
                  SCTs are very competitive in the planetary imaging area. Such imaging uses only the center of the field of view, and if collimation is very accurate, results
                  Message 8 of 26 , Jun 1, 2003
                    SCTs are very competitive in the planetary imaging area. Such imaging uses
                    only the center of the field of view, and if collimation is very accurate,
                    results will be very good. Where SCTs start to fall down is away from the
                    center of the FOV. I have an exceptional 14" SCT (according to folks who
                    have a lot of experience with them; I just know that I'm very happy with the
                    images it takes). But when I try to go to higher resolutions where RCs do a
                    very good job, the SCT doesn't quite have the sharpness in general, and
                    especially away from the center of the FOV. RCs do not have coma (they have
                    a refractor-like slightly-curved field), so they do much better off-axis
                    than SCTs do. The better the seeing, the more likely you are to see these
                    differences show up in the images.

                    I think my C14 can compete on details at the center of the FOV with just
                    about any 12.5" RC image I've seen, but it is clearly inferior away from the
                    center on just about any RC image I've seen, irrespective of aperture.

                    Ron Wodaski
                    author of The New CCD Astronomy
                    http://www.newastro.com


                    -----Original Message-----
                    From: Steve Leikind [mailto:sleikind@...]
                    Sent: Sunday, June 01, 2003 1:27 PM
                    To: ccd-newastro@yahoogroups.com
                    Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200


                    Randy,

                    What you say may well be true, but there are a lot of variables here
                    and it's difficult to separate "the wheat from the chaff". Your SCT
                    undoubtedly didn't have the same kind of optical quality that your
                    Ritchey does. Yet Ed Grafton, Thierry Legault, and Damian Peach have
                    taken some extraordinarily good images of Jupiter and Saturn with
                    their SCT's and I am not sure that I have seen any with Ritchey's
                    that are better even though, for a given aperture, they cost five
                    times to ten times more. Some people claim that those guys were
                    simply lucky to get good SCT's with outstanding optics. Then I've
                    also heard people say that the quality on some of the newer SCT's is
                    generally quite good.

                    Another variable is collimation. It sounds like Legault collimates
                    his 12" every night and often multiple times a night. He has a
                    lengthy discussion about collimation and the effects of
                    miscollimation on his web site and he underlines his main point
                    that "No high resolution result can be hoped without a irreproachable
                    collimation". I wonder how many SCT imagers have collimation that
                    isn't simply good, but "irreproachable"? Every time an SCT
                    mirror "flops" a little, collimation changes with these scopes. I
                    suppose that no wanting to constantly recollimate your scope may
                    justify the cost differential between Ritchey's and SCT's for many.

                    If it's true that there are big differences in the quality of SCT's
                    being produced now, perhaps it makes sense to buy one new from a
                    retailer who accepts returns if you are not satisfied. Then you keep
                    returning them until you find one with superior quality. If you have
                    the patience for this, perhaps you would be rewarded by getting a
                    scope that's as good as a Ritchey (on-axis) at 10% of the cost???

                    It's also possible that people like Legault and Grafton are so much
                    better at taking and processing planetary images that they maximize
                    the potential of their scopes, while people with superior optics have
                    not managed to do that. It would be nice to get the whole story on
                    this, but I am not sure we ever will.

                    Steve

                    --- In ccd-newastro@yahoogroups.com, "Randy Nulman" <rj.nulman@v...>
                    wrote:
                    > I saw the same thing when I got my 12.5 RC. The optics of my old
                    C11
                    > were relatively good, but my fwhm improved by almost 25% with the
                    RC!
                    > (This was comparing "on axis" stars for both scopes)
                    >
                    > I was originally expecting only an "off axis" improvement, but the
                    > quality of the optics in the RCOS really made a difference.
                    >
                    > Randy Nulman
                    >
                    > --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
                    > <yahoo@w...> wrote:
                    > > It has been my experience, both visually and with CCD, that poor
                    > optics are
                    > > more affected by seeing that good optics.
                    > >
                    > > An interesting case in point: On a night of exceptional seeing at
                    > New Mexico
                    > > Skies, I took an image of M51 with the C14 and ST-10 binned 2x2
                    > that was
                    > > very good. Still a little soft, however. In the first tests of
                    the
                    > new 20"
                    > > RC, on a night that was so bad I didn't bother to image with the
                    > C14, the
                    > > images of M51 were as good as they were on that best night with
                    the
                    > C14 -
                    > > despite the fact that we are still making adjustments to the RC
                    and
                    > it's
                    > > mounting to improve performance. This fact just blew me away.
                    > >
                    > > Ron Wodaski
                    > > author of The New CCD Astronomy
                    > > http://www.newastro.com
                    > >
                    > >
                    > > -----Original Message-----
                    > > From: clearviewh [mailto:clearview@c...]
                    > > Sent: Saturday, May 31, 2003 8:13 PM
                    > > To: ccd-newastro@yahoogroups.com
                    > > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
                    > >
                    > >
                    > > To tell you the truth, I think a LOT of it is location. Sometimes
                    I
                    > > whine about not having the money for a nice RC and Paramount mount
                    > > but I have spent plenty on the domed observatory. Thing is, I
                    wonder
                    > > if I would get full value out of that kind of setup here. When
                    > seeing
                    > > is good, which is not that often, I get images that I am very
                    proud
                    > > of. The rest of the time, as I watch the guide star jumping around
                    > > from poor seeing, I wonder just how well even a Paramount would
                    > > perform here.....at least that's what I keep telling myself....
                    LOL
                    > > Ed
                    > >
                    > > --- In ccd-newastro@yahoogroups.com, "Mark de Regt" <deregt@e...>
                    > > wrote:
                    > > > Ed,
                    > > >
                    > > > This is something I have thought a lot about, and talked with
                    > > people with
                    > > > experience with both SCTs and RCs. I believe, of course, that
                    the
                    > > RC optics
                    > > > are better than my LX200, but I also believet that my LX200 has
                    > > excellent
                    > > > optics. When you talk about the RC images you see, it is worth
                    > > keeping in
                    > > > mind that people with RCs tend to be experienced imagers, and
                    > often
                    > > have
                    > > > superior locations. Taking nothing away from Adam Block at Kitt
                    > > Peak (whose
                    > > > images have become routinely sublime, they are so wonderful),
                    and
                    > > others, it
                    > > > is also worth remembering that their scopes are bigger than
                    most
                    > of
                    > > ours.
                    > > > Most of the RCs you see are 12.5 inch, with some at 14.5 inch,
                    16
                    > > inch, and
                    > > > Adam now uses a 20 inch. I know that emulsion photographers say
                    > > that focal
                    > > > ratio is the sole determiner of exposure length, but, with CCD
                    > > imaging of
                    > > > the heavens, I don't believe it--The larger the aperture, the
                    less
                    > > time it
                    > > > takes to get good S/N, I think. Add to that the superior
                    location
                    > > someone
                    > > > like Adam has--no light pollution and 7000 foot elevation, and
                    you
                    > > can't
                    > > > even compare that circumstance to what most of us deal with.
                    Add
                    > > to that
                    > > > the fact the many of the best imagers manage to get several
                    images
                    > > a month
                    > > > (at least), year round, while I'm happy if I get ten in a year;
                    > the
                    > > > experience in image acquisition and image processing, and its
                    > > contribution
                    > > > to the final result, should not be underestimated,
                    > > >
                    > > > I think that the optics themselves plays a pretty minor role in
                    > > what you see
                    > > > with exposure length; the steadier mount is more important, but
                    > the
                    > > AO-7
                    > > > makes up for most of that. I believe that dark skies,
                    elevation,
                    > > and larger
                    > > > aperture has a lot more to do with it than RC quality.
                    > > >
                    > > >
                    > > >
                    > > > > -----Original Message-----
                    > > > > From: clearviewh [mailto:clearview@c...]
                    > > > > Sent: Saturday, May 31, 2003 6:00 PM
                    > > > > To: ccd-newastro@yahoogroups.com
                    > > > > Subject: [ccd-newastro] S/N ; F ratio ; and RC vs LX200
                    > > > >
                    > > > >
                    > > > > Just wanted to take this opportunity, while Ron is apparently
                    > > gone,
                    > > > > to comment on the question of S/N only being related to F.R.
                    I
                    > > have
                    > > > > known for a long time, that with my LX200, I have to take MUCH
                    > > longer
                    > > > > exposure times than someone with say an RC on a Paramount
                    with
                    > the
                    > > > > same FL and diameter. I have gone round and round on the
                    subject
                    > > and
                    > > > > finally deceided that the QUALITY of the setup ALSO plays a
                    role
                    > > in
                    > > > > S/N. Perhaps not, I agree, in the ACTUAL S/N, but a better
                    setup
                    > > > > spreads the signal around less, giving a better image. I have
                    to
                    > > take
                    > > > > a much longer exposures cause the poorer tracking, and
                    optics,
                    > of
                    > > my
                    > > > > LX200, spreads my signal out more..... bloated
                    stars.....etc.
                    > So
                    > > > > when say a Rob Gendler with his 12 in RC at F9 takes a
                    L:R:G:B
                    > of
                    > > > > 120:40:60:60, I have to take a 180:60:90:90 to get an image
                    that
                    > > > > appears to have a similar S/N even at F5....Comments??
                    > > > > Ed
                    > > > >
                    > > > >
                    > > > >
                    > > > > To unsubscribe from this group, send an email to:
                    > > > > ccd-newastro-unsubscribe@egroups.com
                    > > > >
                    > > > >
                    > > > >
                    > > > > Your use of Yahoo! Groups is subject to
                    > > http://docs.yahoo.com/info/terms/
                    > > > >
                    > > > >
                    > >
                    > >
                    > >
                    > > To unsubscribe from this group, send an email to:
                    > > ccd-newastro-unsubscribe@egroups.com
                    > >
                    > >
                    > >
                    > > Your use of Yahoo! Groups is subject to
                    > http://docs.yahoo.com/info/terms/



                    To unsubscribe from this group, send an email to:
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                  • clearviewh
                    I suppose that s why I am more pleased with objects that don t fill more than the center portion of the FOV and seem a little more wide angle than I am with
                    Message 9 of 26 , Jun 1, 2003
                      I suppose that's why I am more pleased with objects that don't fill
                      more than the center portion of the FOV and seem a little more "wide
                      angle" than I am with a try at a high res galaxy that fills the whole
                      frame.....
                      Ed

                      --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
                      <yahoo@w...> wrote:
                      > SCTs are very competitive in the planetary imaging area. Such
                      imaging uses
                      > only the center of the field of view, and if collimation is very
                      accurate,
                      > results will be very good. Where SCTs start to fall down is away
                      from the
                      > center of the FOV. I have an exceptional 14" SCT (according to
                      folks who
                      > have a lot of experience with them; I just know that I'm very happy
                      with the
                      > images it takes). But when I try to go to higher resolutions where
                      RCs do a
                      > very good job, the SCT doesn't quite have the sharpness in general,
                      and
                      > especially away from the center of the FOV. RCs do not have coma
                      (they have
                      > a refractor-like slightly-curved field), so they do much better off-
                      axis
                      > than SCTs do. The better the seeing, the more likely you are to see
                      these
                      > differences show up in the images.
                      >
                      > I think my C14 can compete on details at the center of the FOV with
                      just
                      > about any 12.5" RC image I've seen, but it is clearly inferior away
                      from the
                      > center on just about any RC image I've seen, irrespective of
                      aperture.
                      >
                      > Ron Wodaski
                      > author of The New CCD Astronomy
                      > http://www.newastro.com
                      >
                      >
                      > -----Original Message-----
                      > From: Steve Leikind [mailto:sleikind@v...]
                      > Sent: Sunday, June 01, 2003 1:27 PM
                      > To: ccd-newastro@yahoogroups.com
                      > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
                      >
                      >
                      > Randy,
                      >
                      > What you say may well be true, but there are a lot of variables here
                      > and it's difficult to separate "the wheat from the chaff". Your SCT
                      > undoubtedly didn't have the same kind of optical quality that your
                      > Ritchey does. Yet Ed Grafton, Thierry Legault, and Damian Peach have
                      > taken some extraordinarily good images of Jupiter and Saturn with
                      > their SCT's and I am not sure that I have seen any with Ritchey's
                      > that are better even though, for a given aperture, they cost five
                      > times to ten times more. Some people claim that those guys were
                      > simply lucky to get good SCT's with outstanding optics. Then I've
                      > also heard people say that the quality on some of the newer SCT's is
                      > generally quite good.
                      >
                      > Another variable is collimation. It sounds like Legault collimates
                      > his 12" every night and often multiple times a night. He has a
                      > lengthy discussion about collimation and the effects of
                      > miscollimation on his web site and he underlines his main point
                      > that "No high resolution result can be hoped without a
                      irreproachable
                      > collimation". I wonder how many SCT imagers have collimation that
                      > isn't simply good, but "irreproachable"? Every time an SCT
                      > mirror "flops" a little, collimation changes with these scopes. I
                      > suppose that no wanting to constantly recollimate your scope may
                      > justify the cost differential between Ritchey's and SCT's for many.
                      >
                      > If it's true that there are big differences in the quality of SCT's
                      > being produced now, perhaps it makes sense to buy one new from a
                      > retailer who accepts returns if you are not satisfied. Then you keep
                      > returning them until you find one with superior quality. If you have
                      > the patience for this, perhaps you would be rewarded by getting a
                      > scope that's as good as a Ritchey (on-axis) at 10% of the cost???
                      >
                      > It's also possible that people like Legault and Grafton are so much
                      > better at taking and processing planetary images that they maximize
                      > the potential of their scopes, while people with superior optics
                      have
                      > not managed to do that. It would be nice to get the whole story on
                      > this, but I am not sure we ever will.
                      >
                      > Steve
                      >
                      > --- In ccd-newastro@yahoogroups.com, "Randy Nulman" <rj.nulman@v...>
                      > wrote:
                      > > I saw the same thing when I got my 12.5 RC. The optics of my old
                      > C11
                      > > were relatively good, but my fwhm improved by almost 25% with the
                      > RC!
                      > > (This was comparing "on axis" stars for both scopes)
                      > >
                      > > I was originally expecting only an "off axis" improvement, but the
                      > > quality of the optics in the RCOS really made a difference.
                      > >
                      > > Randy Nulman
                      > >
                      > > --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
                      > > <yahoo@w...> wrote:
                      > > > It has been my experience, both visually and with CCD, that poor
                      > > optics are
                      > > > more affected by seeing that good optics.
                      > > >
                      > > > An interesting case in point: On a night of exceptional seeing
                      at
                      > > New Mexico
                      > > > Skies, I took an image of M51 with the C14 and ST-10 binned 2x2
                      > > that was
                      > > > very good. Still a little soft, however. In the first tests of
                      > the
                      > > new 20"
                      > > > RC, on a night that was so bad I didn't bother to image with the
                      > > C14, the
                      > > > images of M51 were as good as they were on that best night with
                      > the
                      > > C14 -
                      > > > despite the fact that we are still making adjustments to the RC
                      > and
                      > > it's
                      > > > mounting to improve performance. This fact just blew me away.
                      > > >
                      > > > Ron Wodaski
                      > > > author of The New CCD Astronomy
                      > > > http://www.newastro.com
                      > > >
                      > > >
                      > > > -----Original Message-----
                      > > > From: clearviewh [mailto:clearview@c...]
                      > > > Sent: Saturday, May 31, 2003 8:13 PM
                      > > > To: ccd-newastro@yahoogroups.com
                      > > > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
                      > > >
                      > > >
                      > > > To tell you the truth, I think a LOT of it is location.
                      Sometimes
                      > I
                      > > > whine about not having the money for a nice RC and Paramount
                      mount
                      > > > but I have spent plenty on the domed observatory. Thing is, I
                      > wonder
                      > > > if I would get full value out of that kind of setup here. When
                      > > seeing
                      > > > is good, which is not that often, I get images that I am very
                      > proud
                      > > > of. The rest of the time, as I watch the guide star jumping
                      around
                      > > > from poor seeing, I wonder just how well even a Paramount would
                      > > > perform here.....at least that's what I keep telling myself....
                      > LOL
                      > > > Ed
                      > > >
                      > > > --- In ccd-newastro@yahoogroups.com, "Mark de Regt"
                      <deregt@e...>
                      > > > wrote:
                      > > > > Ed,
                      > > > >
                      > > > > This is something I have thought a lot about, and talked with
                      > > > people with
                      > > > > experience with both SCTs and RCs. I believe, of course, that
                      > the
                      > > > RC optics
                      > > > > are better than my LX200, but I also believet that my LX200
                      has
                      > > > excellent
                      > > > > optics. When you talk about the RC images you see, it is
                      worth
                      > > > keeping in
                      > > > > mind that people with RCs tend to be experienced imagers, and
                      > > often
                      > > > have
                      > > > > superior locations. Taking nothing away from Adam Block at
                      Kitt
                      > > > Peak (whose
                      > > > > images have become routinely sublime, they are so wonderful),
                      > and
                      > > > others, it
                      > > > > is also worth remembering that their scopes are bigger than
                      > most
                      > > of
                      > > > ours.
                      > > > > Most of the RCs you see are 12.5 inch, with some at 14.5 inch,
                      > 16
                      > > > inch, and
                      > > > > Adam now uses a 20 inch. I know that emulsion photographers
                      say
                      > > > that focal
                      > > > > ratio is the sole determiner of exposure length, but, with CCD
                      > > > imaging of
                      > > > > the heavens, I don't believe it--The larger the aperture, the
                      > less
                      > > > time it
                      > > > > takes to get good S/N, I think. Add to that the superior
                      > location
                      > > > someone
                      > > > > like Adam has--no light pollution and 7000 foot elevation, and
                      > you
                      > > > can't
                      > > > > even compare that circumstance to what most of us deal with.
                      > Add
                      > > > to that
                      > > > > the fact the many of the best imagers manage to get several
                      > images
                      > > > a month
                      > > > > (at least), year round, while I'm happy if I get ten in a
                      year;
                      > > the
                      > > > > experience in image acquisition and image processing, and its
                      > > > contribution
                      > > > > to the final result, should not be underestimated,
                      > > > >
                      > > > > I think that the optics themselves plays a pretty minor role
                      in
                      > > > what you see
                      > > > > with exposure length; the steadier mount is more important,
                      but
                      > > the
                      > > > AO-7
                      > > > > makes up for most of that. I believe that dark skies,
                      > elevation,
                      > > > and larger
                      > > > > aperture has a lot more to do with it than RC quality.
                      > > > >
                      > > > >
                      > > > >
                      > > > > > -----Original Message-----
                      > > > > > From: clearviewh [mailto:clearview@c...]
                      > > > > > Sent: Saturday, May 31, 2003 6:00 PM
                      > > > > > To: ccd-newastro@yahoogroups.com
                      > > > > > Subject: [ccd-newastro] S/N ; F ratio ; and RC vs LX200
                      > > > > >
                      > > > > >
                      > > > > > Just wanted to take this opportunity, while Ron is
                      apparently
                      > > > gone,
                      > > > > > to comment on the question of S/N only being related to F.R.
                      > I
                      > > > have
                      > > > > > known for a long time, that with my LX200, I have to take
                      MUCH
                      > > > longer
                      > > > > > exposure times than someone with say an RC on a Paramount
                      > with
                      > > the
                      > > > > > same FL and diameter. I have gone round and round on the
                      > subject
                      > > > and
                      > > > > > finally deceided that the QUALITY of the setup ALSO plays a
                      > role
                      > > > in
                      > > > > > S/N. Perhaps not, I agree, in the ACTUAL S/N, but a better
                      > setup
                      > > > > > spreads the signal around less, giving a better image. I
                      have
                      > to
                      > > > take
                      > > > > > a much longer exposures cause the poorer tracking, and
                      > optics,
                      > > of
                      > > > my
                      > > > > > LX200, spreads my signal out more..... bloated
                      > stars.....etc.
                      > > So
                      > > > > > when say a Rob Gendler with his 12 in RC at F9 takes a
                      > L:R:G:B
                      > > of
                      > > > > > 120:40:60:60, I have to take a 180:60:90:90 to get an image
                      > that
                      > > > > > appears to have a similar S/N even at F5....Comments??
                      > > > > > Ed
                      > > > > >
                      > > > > >
                      > > > > >
                      > > > > > To unsubscribe from this group, send an email to:
                      > > > > > ccd-newastro-unsubscribe@egroups.com
                      > > > > >
                      > > > > >
                      > > > > >
                      > > > > > Your use of Yahoo! Groups is subject to
                      > > > http://docs.yahoo.com/info/terms/
                      > > > > >
                      > > > > >
                      > > >
                      > > >
                      > > >
                      > > > To unsubscribe from this group, send an email to:
                      > > > ccd-newastro-unsubscribe@egroups.com
                      > > >
                      > > >
                      > > >
                      > > > Your use of Yahoo! Groups is subject to
                      > > http://docs.yahoo.com/info/terms/
                      >
                      >
                      >
                      > To unsubscribe from this group, send an email to:
                      > ccd-newastro-unsubscribe@egroups.com
                      >
                      >
                      >
                      > Your use of Yahoo! Groups is subject to
                      http://docs.yahoo.com/info/terms/
                    • Steve Leikind
                      Ron, This makes sense. It would be nice to know how much variability there is in the quality of SCT s at this time, but any information we can get about this
                      Message 10 of 26 , Jun 1, 2003
                        Ron,

                        This makes sense. It would be nice to know how much variability there
                        is in the quality of SCT's at this time, but any information we can
                        get about this is probably anecdotal. Obviously, you managed to get
                        an SCT which others regard as among the cream of the crop.

                        I am curious as to how Mewlon's and other designs (Mak-Newt; Mak-
                        Cass) compete with Ritchey's on-axis and off. I have read claims that
                        Ritchey's do not produce the best on-axis images, but I cannot
                        remember where. Obviously, there are trade-offs with some of the
                        other designs such as f-ratio, bulk etc. where Ritchey's have an edge.

                        Steve

                        --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
                        <yahoo@w...> wrote:
                        > SCTs are very competitive in the planetary imaging area. Such
                        imaging uses
                        > only the center of the field of view, and if collimation is very
                        accurate,
                        > results will be very good. Where SCTs start to fall down is away
                        from the
                        > center of the FOV. I have an exceptional 14" SCT (according to
                        folks who
                        > have a lot of experience with them; I just know that I'm very happy
                        with the
                        > images it takes). But when I try to go to higher resolutions where
                        RCs do a
                        > very good job, the SCT doesn't quite have the sharpness in general,
                        and
                        > especially away from the center of the FOV. RCs do not have coma
                        (they have
                        > a refractor-like slightly-curved field), so they do much better off-
                        axis
                        > than SCTs do. The better the seeing, the more likely you are to see
                        these
                        > differences show up in the images.
                        >
                        > I think my C14 can compete on details at the center of the FOV with
                        just
                        > about any 12.5" RC image I've seen, but it is clearly inferior away
                        from the
                        > center on just about any RC image I've seen, irrespective of
                        aperture.
                        >
                        > Ron Wodaski
                        > author of The New CCD Astronomy
                        > http://www.newastro.com
                        >
                        >
                        > -----Original Message-----
                        > From: Steve Leikind [mailto:sleikind@v...]
                        > Sent: Sunday, June 01, 2003 1:27 PM
                        > To: ccd-newastro@yahoogroups.com
                        > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
                        >
                        >
                        > Randy,
                        >
                        > What you say may well be true, but there are a lot of variables here
                        > and it's difficult to separate "the wheat from the chaff". Your SCT
                        > undoubtedly didn't have the same kind of optical quality that your
                        > Ritchey does. Yet Ed Grafton, Thierry Legault, and Damian Peach have
                        > taken some extraordinarily good images of Jupiter and Saturn with
                        > their SCT's and I am not sure that I have seen any with Ritchey's
                        > that are better even though, for a given aperture, they cost five
                        > times to ten times more. Some people claim that those guys were
                        > simply lucky to get good SCT's with outstanding optics. Then I've
                        > also heard people say that the quality on some of the newer SCT's is
                        > generally quite good.
                        >
                        > Another variable is collimation. It sounds like Legault collimates
                        > his 12" every night and often multiple times a night. He has a
                        > lengthy discussion about collimation and the effects of
                        > miscollimation on his web site and he underlines his main point
                        > that "No high resolution result can be hoped without a
                        irreproachable
                        > collimation". I wonder how many SCT imagers have collimation that
                        > isn't simply good, but "irreproachable"? Every time an SCT
                        > mirror "flops" a little, collimation changes with these scopes. I
                        > suppose that no wanting to constantly recollimate your scope may
                        > justify the cost differential between Ritchey's and SCT's for many.
                        >
                        > If it's true that there are big differences in the quality of SCT's
                        > being produced now, perhaps it makes sense to buy one new from a
                        > retailer who accepts returns if you are not satisfied. Then you keep
                        > returning them until you find one with superior quality. If you have
                        > the patience for this, perhaps you would be rewarded by getting a
                        > scope that's as good as a Ritchey (on-axis) at 10% of the cost???
                        >
                        > It's also possible that people like Legault and Grafton are so much
                        > better at taking and processing planetary images that they maximize
                        > the potential of their scopes, while people with superior optics
                        have
                        > not managed to do that. It would be nice to get the whole story on
                        > this, but I am not sure we ever will.
                        >
                        > Steve
                        >
                        > --- In ccd-newastro@yahoogroups.com, "Randy Nulman" <rj.nulman@v...>
                        > wrote:
                        > > I saw the same thing when I got my 12.5 RC. The optics of my old
                        > C11
                        > > were relatively good, but my fwhm improved by almost 25% with the
                        > RC!
                        > > (This was comparing "on axis" stars for both scopes)
                        > >
                        > > I was originally expecting only an "off axis" improvement, but the
                        > > quality of the optics in the RCOS really made a difference.
                        > >
                        > > Randy Nulman
                        > >
                        > > --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
                        > > <yahoo@w...> wrote:
                        > > > It has been my experience, both visually and with CCD, that poor
                        > > optics are
                        > > > more affected by seeing that good optics.
                        > > >
                        > > > An interesting case in point: On a night of exceptional seeing
                        at
                        > > New Mexico
                        > > > Skies, I took an image of M51 with the C14 and ST-10 binned 2x2
                        > > that was
                        > > > very good. Still a little soft, however. In the first tests of
                        > the
                        > > new 20"
                        > > > RC, on a night that was so bad I didn't bother to image with the
                        > > C14, the
                        > > > images of M51 were as good as they were on that best night with
                        > the
                        > > C14 -
                        > > > despite the fact that we are still making adjustments to the RC
                        > and
                        > > it's
                        > > > mounting to improve performance. This fact just blew me away.
                        > > >
                        > > > Ron Wodaski
                        > > > author of The New CCD Astronomy
                        > > > http://www.newastro.com
                        > > >
                        > > >
                        > > > -----Original Message-----
                        > > > From: clearviewh [mailto:clearview@c...]
                        > > > Sent: Saturday, May 31, 2003 8:13 PM
                        > > > To: ccd-newastro@yahoogroups.com
                        > > > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
                        > > >
                        > > >
                        > > > To tell you the truth, I think a LOT of it is location.
                        Sometimes
                        > I
                        > > > whine about not having the money for a nice RC and Paramount
                        mount
                        > > > but I have spent plenty on the domed observatory. Thing is, I
                        > wonder
                        > > > if I would get full value out of that kind of setup here. When
                        > > seeing
                        > > > is good, which is not that often, I get images that I am very
                        > proud
                        > > > of. The rest of the time, as I watch the guide star jumping
                        around
                        > > > from poor seeing, I wonder just how well even a Paramount would
                        > > > perform here.....at least that's what I keep telling myself....
                        > LOL
                        > > > Ed
                        > > >
                        > > > --- In ccd-newastro@yahoogroups.com, "Mark de Regt"
                        <deregt@e...>
                        > > > wrote:
                        > > > > Ed,
                        > > > >
                        > > > > This is something I have thought a lot about, and talked with
                        > > > people with
                        > > > > experience with both SCTs and RCs. I believe, of course, that
                        > the
                        > > > RC optics
                        > > > > are better than my LX200, but I also believet that my LX200
                        has
                        > > > excellent
                        > > > > optics. When you talk about the RC images you see, it is
                        worth
                        > > > keeping in
                        > > > > mind that people with RCs tend to be experienced imagers, and
                        > > often
                        > > > have
                        > > > > superior locations. Taking nothing away from Adam Block at
                        Kitt
                        > > > Peak (whose
                        > > > > images have become routinely sublime, they are so wonderful),
                        > and
                        > > > others, it
                        > > > > is also worth remembering that their scopes are bigger than
                        > most
                        > > of
                        > > > ours.
                        > > > > Most of the RCs you see are 12.5 inch, with some at 14.5 inch,
                        > 16
                        > > > inch, and
                        > > > > Adam now uses a 20 inch. I know that emulsion photographers
                        say
                        > > > that focal
                        > > > > ratio is the sole determiner of exposure length, but, with CCD
                        > > > imaging of
                        > > > > the heavens, I don't believe it--The larger the aperture, the
                        > less
                        > > > time it
                        > > > > takes to get good S/N, I think. Add to that the superior
                        > location
                        > > > someone
                        > > > > like Adam has--no light pollution and 7000 foot elevation, and
                        > you
                        > > > can't
                        > > > > even compare that circumstance to what most of us deal with.
                        > Add
                        > > > to that
                        > > > > the fact the many of the best imagers manage to get several
                        > images
                        > > > a month
                        > > > > (at least), year round, while I'm happy if I get ten in a
                        year;
                        > > the
                        > > > > experience in image acquisition and image processing, and its
                        > > > contribution
                        > > > > to the final result, should not be underestimated,
                        > > > >
                        > > > > I think that the optics themselves plays a pretty minor role
                        in
                        > > > what you see
                        > > > > with exposure length; the steadier mount is more important,
                        but
                        > > the
                        > > > AO-7
                        > > > > makes up for most of that. I believe that dark skies,
                        > elevation,
                        > > > and larger
                        > > > > aperture has a lot more to do with it than RC quality.
                        > > > >
                        > > > >
                        > > > >
                        > > > > > -----Original Message-----
                        > > > > > From: clearviewh [mailto:clearview@c...]
                        > > > > > Sent: Saturday, May 31, 2003 6:00 PM
                        > > > > > To: ccd-newastro@yahoogroups.com
                        > > > > > Subject: [ccd-newastro] S/N ; F ratio ; and RC vs LX200
                        > > > > >
                        > > > > >
                        > > > > > Just wanted to take this opportunity, while Ron is
                        apparently
                        > > > gone,
                        > > > > > to comment on the question of S/N only being related to F.R.
                        > I
                        > > > have
                        > > > > > known for a long time, that with my LX200, I have to take
                        MUCH
                        > > > longer
                        > > > > > exposure times than someone with say an RC on a Paramount
                        > with
                        > > the
                        > > > > > same FL and diameter. I have gone round and round on the
                        > subject
                        > > > and
                        > > > > > finally deceided that the QUALITY of the setup ALSO plays a
                        > role
                        > > > in
                        > > > > > S/N. Perhaps not, I agree, in the ACTUAL S/N, but a better
                        > setup
                        > > > > > spreads the signal around less, giving a better image. I
                        have
                        > to
                        > > > take
                        > > > > > a much longer exposures cause the poorer tracking, and
                        > optics,
                        > > of
                        > > > my
                        > > > > > LX200, spreads my signal out more..... bloated
                        > stars.....etc.
                        > > So
                        > > > > > when say a Rob Gendler with his 12 in RC at F9 takes a
                        > L:R:G:B
                        > > of
                        > > > > > 120:40:60:60, I have to take a 180:60:90:90 to get an image
                        > that
                        > > > > > appears to have a similar S/N even at F5....Comments??
                        > > > > > Ed
                        > > > > >
                        > > > > >
                        > > > > >
                        > > > > > To unsubscribe from this group, send an email to:
                        > > > > > ccd-newastro-unsubscribe@egroups.com
                        > > > > >
                        > > > > >
                        > > > > >
                        > > > > > Your use of Yahoo! Groups is subject to
                        > > > http://docs.yahoo.com/info/terms/
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                        > > > > >
                        > > >
                        > > >
                        > > >
                        > > > To unsubscribe from this group, send an email to:
                        > > > ccd-newastro-unsubscribe@egroups.com
                        > > >
                        > > >
                        > > >
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                        >
                        >
                        >
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                      • Chris Johnston
                        Gents All very interesting comments. It seems that excellent on axis images are taken by the experts mentioned, although I note that Damian Peach is now buying
                        Message 11 of 26 , Jun 1, 2003
                          Gents

                          All very interesting comments.

                          It seems that excellent on axis images are taken by the experts
                          mentioned, although I note that Damian Peach is now buying a Mewlon
                          250. From what I have read and seen it appears that to get good
                          images from a commercial SCT, assuming you get reasonable optics in
                          the first instance, you need to collimate continuously as well as
                          correct for mirror flop.

                          However, for those of us who have no wish to continuously collimate
                          and who have no wish to combat mirror flop, the Mewlon is a
                          compromise between the commercial SCT and the expensive RC. If will
                          give equal on axis performance but has about the same coma off axis
                          as the SCT. Of course there is also just about 100% assurance of
                          getting a good scope out of the box.

                          The comment that ten times the price should bring ten times the
                          quality of images was interesting, as this would not be paralleled in
                          any other capital items. Take for instance a motor vehicle. Does
                          the BMW give the commensurate amount of quality as compared to the
                          mass produced sedan. Nowhere near it I would have thought. Yet
                          there is an active market for BMWs. It appears that there is no
                          shortage of people who will pay that singificant amount more for the
                          small amount of extra quality. Hell, I am one of them.

                          Cheers
                          Chris
                        • clearviewh
                          It appears that there is no ... the ... Ah lets celebrate our differences then, for I am not LOL course my Toyato truck cost 17,000. I wouldn t pay 170,000
                          Message 12 of 26 , Jun 2, 2003
                            It appears that there is no
                            > shortage of people who will pay that singificant amount more for
                            the
                            > small amount of extra quality. Hell, I am one of them.
                            >
                            > Cheers
                            > Chris

                            Ah lets celebrate our differences then, for I am not LOL
                            course my Toyato truck cost 17,000. I wouldn't pay 170,000 for
                            just a slightly better one :<)
                            Ed
                          • clearviewh
                            ... .....course it s not THAT much of a battle, last nights precollamtion took 4 minutes, and the lock for the mirror cost 18.00 not bad investment to save
                            Message 13 of 26 , Jun 2, 2003
                              >
                              > However, for those of us who have no wish to continuously collimate
                              > and who have no wish to combat mirror flop,
                              .....course it's not THAT much of a battle, last nights
                              precollamtion took 4 minutes, and the lock for the mirror cost 18.00
                              not bad investment to save 20,000 and look at what I got for my
                              trouble
                              http://www.cuttingedge.net/~clearview/images/m27.htm
                            • Chris Johnston
                              Ed In regard to the Toyota I would agree with you. My Toyota 4 wheel drive cost new not much more than your truck. Yet I often see many Lexus 4 wheel drives
                              Message 14 of 26 , Jun 2, 2003
                                Ed

                                In regard to the Toyota I would agree with you. My Toyota 4 wheel
                                drive cost new not much more than your truck. Yet I often see many
                                Lexus 4 wheel drives around the place that cost four times as much.
                                Damned if I can make out the difference.

                                Chris
                              • Wodaski Yahoo account
                                I think there is less variability than in the past, but I do not know how one could quantify it because most of the data is, as you note, anecdotal. The
                                Message 15 of 26 , Jun 3, 2003
                                  I think there is less variability than in the past, but I do not know how
                                  one could quantify it because most of the data is, as you note, anecdotal.

                                  The Mewlons are very good optically. They have coma, like most Cassegrain
                                  designs, but have superb on-axis and near-axis performance. They are very
                                  refractor-like, with just a shade less contrast than a superb refractor.
                                  Last I looked, however, 8-10" refractors were, um, a bit more expensive than
                                  a Mewlon. <g>

                                  I can see where a Ritchie might not have the absolute best on-axis
                                  performance since it is optimized for overall field performance. But it's
                                  still very good. A high-end Newtonian might do better at central spot size,
                                  but of course fast Newt's have really noticeable coma. The difference with
                                  the Ritchie-Chretien is that it uses hyperbolic (instead of the more easily
                                  made spherical or parabolic) mirrors. This allows designs that eliminate
                                  coma.

                                  For really large flat fields, an RC requires a corrector (just as a high-end
                                  refractor might require a flattener). But for most CCD chips, flatness of
                                  field is not an issue. Larger film formats require a corrector, such as that
                                  found on the Takahashi BRC.

                                  Ron Wodaski
                                  author of The New CCD Astronomy
                                  http://www.newastro.com


                                  -----Original Message-----
                                  From: Steve Leikind [mailto:sleikind@...]
                                  Sent: Sunday, June 01, 2003 4:46 PM
                                  To: ccd-newastro@yahoogroups.com
                                  Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200


                                  Ron,

                                  This makes sense. It would be nice to know how much variability there
                                  is in the quality of SCT's at this time, but any information we can
                                  get about this is probably anecdotal. Obviously, you managed to get
                                  an SCT which others regard as among the cream of the crop.

                                  I am curious as to how Mewlon's and other designs (Mak-Newt; Mak-
                                  Cass) compete with Ritchey's on-axis and off. I have read claims that
                                  Ritchey's do not produce the best on-axis images, but I cannot
                                  remember where. Obviously, there are trade-offs with some of the
                                  other designs such as f-ratio, bulk etc. where Ritchey's have an edge.

                                  Steve

                                  --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
                                  <yahoo@w...> wrote:
                                  > SCTs are very competitive in the planetary imaging area. Such
                                  imaging uses
                                  > only the center of the field of view, and if collimation is very
                                  accurate,
                                  > results will be very good. Where SCTs start to fall down is away
                                  from the
                                  > center of the FOV. I have an exceptional 14" SCT (according to
                                  folks who
                                  > have a lot of experience with them; I just know that I'm very happy
                                  with the
                                  > images it takes). But when I try to go to higher resolutions where
                                  RCs do a
                                  > very good job, the SCT doesn't quite have the sharpness in general,
                                  and
                                  > especially away from the center of the FOV. RCs do not have coma
                                  (they have
                                  > a refractor-like slightly-curved field), so they do much better off-
                                  axis
                                  > than SCTs do. The better the seeing, the more likely you are to see
                                  these
                                  > differences show up in the images.
                                  >
                                  > I think my C14 can compete on details at the center of the FOV with
                                  just
                                  > about any 12.5" RC image I've seen, but it is clearly inferior away
                                  from the
                                  > center on just about any RC image I've seen, irrespective of
                                  aperture.
                                  >
                                  > Ron Wodaski
                                  > author of The New CCD Astronomy
                                  > http://www.newastro.com
                                  >
                                  >
                                  > -----Original Message-----
                                  > From: Steve Leikind [mailto:sleikind@v...]
                                  > Sent: Sunday, June 01, 2003 1:27 PM
                                  > To: ccd-newastro@yahoogroups.com
                                  > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
                                  >
                                  >
                                  > Randy,
                                  >
                                  > What you say may well be true, but there are a lot of variables here
                                  > and it's difficult to separate "the wheat from the chaff". Your SCT
                                  > undoubtedly didn't have the same kind of optical quality that your
                                  > Ritchey does. Yet Ed Grafton, Thierry Legault, and Damian Peach have
                                  > taken some extraordinarily good images of Jupiter and Saturn with
                                  > their SCT's and I am not sure that I have seen any with Ritchey's
                                  > that are better even though, for a given aperture, they cost five
                                  > times to ten times more. Some people claim that those guys were
                                  > simply lucky to get good SCT's with outstanding optics. Then I've
                                  > also heard people say that the quality on some of the newer SCT's is
                                  > generally quite good.
                                  >
                                  > Another variable is collimation. It sounds like Legault collimates
                                  > his 12" every night and often multiple times a night. He has a
                                  > lengthy discussion about collimation and the effects of
                                  > miscollimation on his web site and he underlines his main point
                                  > that "No high resolution result can be hoped without a
                                  irreproachable
                                  > collimation". I wonder how many SCT imagers have collimation that
                                  > isn't simply good, but "irreproachable"? Every time an SCT
                                  > mirror "flops" a little, collimation changes with these scopes. I
                                  > suppose that no wanting to constantly recollimate your scope may
                                  > justify the cost differential between Ritchey's and SCT's for many.
                                  >
                                  > If it's true that there are big differences in the quality of SCT's
                                  > being produced now, perhaps it makes sense to buy one new from a
                                  > retailer who accepts returns if you are not satisfied. Then you keep
                                  > returning them until you find one with superior quality. If you have
                                  > the patience for this, perhaps you would be rewarded by getting a
                                  > scope that's as good as a Ritchey (on-axis) at 10% of the cost???
                                  >
                                  > It's also possible that people like Legault and Grafton are so much
                                  > better at taking and processing planetary images that they maximize
                                  > the potential of their scopes, while people with superior optics
                                  have
                                  > not managed to do that. It would be nice to get the whole story on
                                  > this, but I am not sure we ever will.
                                  >
                                  > Steve
                                  >
                                  > --- In ccd-newastro@yahoogroups.com, "Randy Nulman" <rj.nulman@v...>
                                  > wrote:
                                  > > I saw the same thing when I got my 12.5 RC. The optics of my old
                                  > C11
                                  > > were relatively good, but my fwhm improved by almost 25% with the
                                  > RC!
                                  > > (This was comparing "on axis" stars for both scopes)
                                  > >
                                  > > I was originally expecting only an "off axis" improvement, but the
                                  > > quality of the optics in the RCOS really made a difference.
                                  > >
                                  > > Randy Nulman
                                  > >
                                  > > --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo account"
                                  > > <yahoo@w...> wrote:
                                  > > > It has been my experience, both visually and with CCD, that poor
                                  > > optics are
                                  > > > more affected by seeing that good optics.
                                  > > >
                                  > > > An interesting case in point: On a night of exceptional seeing
                                  at
                                  > > New Mexico
                                  > > > Skies, I took an image of M51 with the C14 and ST-10 binned 2x2
                                  > > that was
                                  > > > very good. Still a little soft, however. In the first tests of
                                  > the
                                  > > new 20"
                                  > > > RC, on a night that was so bad I didn't bother to image with the
                                  > > C14, the
                                  > > > images of M51 were as good as they were on that best night with
                                  > the
                                  > > C14 -
                                  > > > despite the fact that we are still making adjustments to the RC
                                  > and
                                  > > it's
                                  > > > mounting to improve performance. This fact just blew me away.
                                  > > >
                                  > > > Ron Wodaski
                                  > > > author of The New CCD Astronomy
                                  > > > http://www.newastro.com
                                  > > >
                                  > > >
                                  > > > -----Original Message-----
                                  > > > From: clearviewh [mailto:clearview@c...]
                                  > > > Sent: Saturday, May 31, 2003 8:13 PM
                                  > > > To: ccd-newastro@yahoogroups.com
                                  > > > Subject: [ccd-newastro] Re: S/N ; F ratio ; and RC vs LX200
                                  > > >
                                  > > >
                                  > > > To tell you the truth, I think a LOT of it is location.
                                  Sometimes
                                  > I
                                  > > > whine about not having the money for a nice RC and Paramount
                                  mount
                                  > > > but I have spent plenty on the domed observatory. Thing is, I
                                  > wonder
                                  > > > if I would get full value out of that kind of setup here. When
                                  > > seeing
                                  > > > is good, which is not that often, I get images that I am very
                                  > proud
                                  > > > of. The rest of the time, as I watch the guide star jumping
                                  around
                                  > > > from poor seeing, I wonder just how well even a Paramount would
                                  > > > perform here.....at least that's what I keep telling myself....
                                  > LOL
                                  > > > Ed
                                  > > >
                                  > > > --- In ccd-newastro@yahoogroups.com, "Mark de Regt"
                                  <deregt@e...>
                                  > > > wrote:
                                  > > > > Ed,
                                  > > > >
                                  > > > > This is something I have thought a lot about, and talked with
                                  > > > people with
                                  > > > > experience with both SCTs and RCs. I believe, of course, that
                                  > the
                                  > > > RC optics
                                  > > > > are better than my LX200, but I also believet that my LX200
                                  has
                                  > > > excellent
                                  > > > > optics. When you talk about the RC images you see, it is
                                  worth
                                  > > > keeping in
                                  > > > > mind that people with RCs tend to be experienced imagers, and
                                  > > often
                                  > > > have
                                  > > > > superior locations. Taking nothing away from Adam Block at
                                  Kitt
                                  > > > Peak (whose
                                  > > > > images have become routinely sublime, they are so wonderful),
                                  > and
                                  > > > others, it
                                  > > > > is also worth remembering that their scopes are bigger than
                                  > most
                                  > > of
                                  > > > ours.
                                  > > > > Most of the RCs you see are 12.5 inch, with some at 14.5 inch,
                                  > 16
                                  > > > inch, and
                                  > > > > Adam now uses a 20 inch. I know that emulsion photographers
                                  say
                                  > > > that focal
                                  > > > > ratio is the sole determiner of exposure length, but, with CCD
                                  > > > imaging of
                                  > > > > the heavens, I don't believe it--The larger the aperture, the
                                  > less
                                  > > > time it
                                  > > > > takes to get good S/N, I think. Add to that the superior
                                  > location
                                  > > > someone
                                  > > > > like Adam has--no light pollution and 7000 foot elevation, and
                                  > you
                                  > > > can't
                                  > > > > even compare that circumstance to what most of us deal with.
                                  > Add
                                  > > > to that
                                  > > > > the fact the many of the best imagers manage to get several
                                  > images
                                  > > > a month
                                  > > > > (at least), year round, while I'm happy if I get ten in a
                                  year;
                                  > > the
                                  > > > > experience in image acquisition and image processing, and its
                                  > > > contribution
                                  > > > > to the final result, should not be underestimated,
                                  > > > >
                                  > > > > I think that the optics themselves plays a pretty minor role
                                  in
                                  > > > what you see
                                  > > > > with exposure length; the steadier mount is more important,
                                  but
                                  > > the
                                  > > > AO-7
                                  > > > > makes up for most of that. I believe that dark skies,
                                  > elevation,
                                  > > > and larger
                                  > > > > aperture has a lot more to do with it than RC quality.
                                  > > > >
                                  > > > >
                                  > > > >
                                  > > > > > -----Original Message-----
                                  > > > > > From: clearviewh [mailto:clearview@c...]
                                  > > > > > Sent: Saturday, May 31, 2003 6:00 PM
                                  > > > > > To: ccd-newastro@yahoogroups.com
                                  > > > > > Subject: [ccd-newastro] S/N ; F ratio ; and RC vs LX200
                                  > > > > >
                                  > > > > >
                                  > > > > > Just wanted to take this opportunity, while Ron is
                                  apparently
                                  > > > gone,
                                  > > > > > to comment on the question of S/N only being related to F.R.
                                  > I
                                  > > > have
                                  > > > > > known for a long time, that with my LX200, I have to take
                                  MUCH
                                  > > > longer
                                  > > > > > exposure times than someone with say an RC on a Paramount
                                  > with
                                  > > the
                                  > > > > > same FL and diameter. I have gone round and round on the
                                  > subject
                                  > > > and
                                  > > > > > finally deceided that the QUALITY of the setup ALSO plays a
                                  > role
                                  > > > in
                                  > > > > > S/N. Perhaps not, I agree, in the ACTUAL S/N, but a better
                                  > setup
                                  > > > > > spreads the signal around less, giving a better image. I
                                  have
                                  > to
                                  > > > take
                                  > > > > > a much longer exposures cause the poorer tracking, and
                                  > optics,
                                  > > of
                                  > > > my
                                  > > > > > LX200, spreads my signal out more..... bloated
                                  > stars.....etc.
                                  > > So
                                  > > > > > when say a Rob Gendler with his 12 in RC at F9 takes a
                                  > L:R:G:B
                                  > > of
                                  > > > > > 120:40:60:60, I have to take a 180:60:90:90 to get an image
                                  > that
                                  > > > > > appears to have a similar S/N even at F5....Comments??
                                  > > > > > Ed
                                  > > > > >
                                  > > > > >
                                  > > > > >
                                  > > > > > To unsubscribe from this group, send an email to:
                                  > > > > > ccd-newastro-unsubscribe@egroups.com
                                  > > > > >
                                  > > > > >
                                  > > > > >
                                  > > > > > Your use of Yahoo! Groups is subject to
                                  > > > http://docs.yahoo.com/info/terms/
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                                  > > > > >
                                  > > >
                                  > > >
                                  > > >
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                                  > > >
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