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RE: [William-Optics] Re: Wm-Optics 2" Diagonal

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  • Kent Gittings
    That s actually good. The dielectric coatings severely degrade the wave front error in the TV and AP diagonals. While it may make them last longer and makes
    Message 1 of 20 , Aug 9, 2001
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      That's actually good. The dielectric coatings severely degrade the wave
      front error in the TV and AP diagonals. While it may make them last longer
      and makes them brighter, a mirror that starts out as good as 1/25 wave will
      end up around 1/6 or so once the entire dielectric layer stack is layered
      on. Any small imperfection in the thickness of a layer gets magnified the
      more layers you put on top of it. I think Vernonscope actually experimented
      with this several years ago and decided against using a dielectric coating
      because it severely compromised the surface error on the final product. And
      they were using 1/40 wave mirrors also.
      One reason the TV and AP diagonals appear so good is that they are very
      careful about aligning the mirrors to be as perfectly on axis as possible.
      This will make them appear much better than the average one that maybe off
      slightly. Try setting up a set of optics (SCT/Mak )with as perfect an
      alignment as you can get with a laser collimator. Then stick every diagonal
      you can get in there with the laser on it and you'd be surprised how many
      you have access to that may be off alignment (or may have machining errors
      in the tubes). Even good ones. One of the best aligned diagonals is the
      Celestron prism diagonal that comes with the scopes. And most guys switch to
      a mirror because it's "better" early on. I've seen so many cases where I've
      had them tell me about problems that I often ask if they still have the
      original one and then in just about every case I find that the mirror
      diagonal they replaced it with has an alignment problem. My recommendation
      is to test every one you are going to buy as even a small alignment error
      will make the focal plane twisted slightly and reduce performance.
      Kent Gittings

      -----Original Message-----
      From: Ray York [mailto:ray@...]
      Sent: Thursday, August 09, 2001 1:02 AM
      To: William-Optics@yahoogroups.com
      Subject: RE: [William-Optics] Re: Wm-Optics 2" Diagonal


      Just for clarification, the WO diagonal is NOT dielectrically coated like
      the TV and AP diagonals are.

      Ray York
      Anacortes Telescope and Wild Bird
      http://www.BuyTelescopes.com/
      http://www.AstroMart.com/
      (800) 850-2001

      -----Original Message-----
      From: Don Wyman [mailto:dwyman@...]
      Sent: Wednesday, August 08, 2001 8:35 PM
      To: William-Optics@yahoogroups.com
      Subject: [William-Optics] Re: Wm-Optics 2" Diagonal

      --- In William-Optics@y..., "Dan and Carol" <poziovahim@l...> wrote:
      > Hey Don! I have the one that came with the Megrez 80 and Its a
      beaut! I
      > like the silver side plates rather than the black too! Bueno, Dan

      Thanks Dan. With all the talk about enhanced mirror diagonals like the
      TV Everbrite and the AP version, it's nice to see one that doesn't
      cost an arm and a leg.

      Don



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    • Moravianus@yahoo.com
      I would like to find out, what is the optical path length of this diagonal and what is the length of the piece you insert into focuser tube. Thanks for help.
      Message 2 of 20 , Aug 9, 2001
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        I would like to find out, what is the optical path length of this
        diagonal and what is the length of the piece you insert into focuser tube.

        Thanks for help.

        David
      • Dan and Carol
        Yeah it does! The focuser is really sweet too! I just got my cable for connecting the ss2k to my STV! Tomorrow nite I finally get to put the whole thing
        Message 3 of 20 , Aug 9, 2001
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          Yeah it does! The focuser is really sweet too! I just got my cable for
          connecting the ss2k to my STV! Tomorrow nite I finally get to put the whole
          thing together for the first time! If all works good I'll finally be able
          to shoot some film. Buen cielo, Dan
          -----Original Message-----
          From: Don Wyman <dwyman@...>
          To: William-Optics@yahoogroups.com <William-Optics@yahoogroups.com>
          Date: Thursday, August 09, 2001 9:16 AM
          Subject: [William-Optics] Re: Wm-Optics 2" Diagonal


          >--- In William-Optics@y..., "Dan and Carol" <poziovahim@l...> wrote:
          >> Yeah, I have the Televue also but now I mostly use the WO! Them
          >side pieces
          >> are like,like Mags man! You know? I mean, Que No! Bueno, Dan NM
          >
          >
          >Heh, yeah. The whole WO line catches your eye. That Meg 80 looks sweet
          >too. Of course when you buy the Meg 80 that 2" enhanced diagonal comes
          >with it right?
          >
          >Don
          >
          >
          >
          >To unsubscribe from this group, send an email to:
          >William-Optics-unsubscribe@yahoogroups.com
          >
          >
          >
          >
          >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
          >
        • Markus Ludes
          Hi kent, your infos are not completed. A 99% coating decrease the wave surface area on full surface,it makes an high edge, but the center remains perfect, and
          Message 4 of 20 , Aug 10, 2001
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            Hi kent,

            your infos are not completed.

            A 99% coating decrease the wave surface area on full surface,it makes an
            high edge, but the center remains perfect, and only the cente ris used by
            high powers.The edge which is not such good is used only by low powers.
            A 96% coating does not decrease at all any of the surface, if right made

            best wishes

            Markus
            ----- Original Message -----
            From: "Kent Gittings" <kent@...>
            To: <William-Optics@yahoogroups.com>
            Sent: Thursday, August 09, 2001 5:10 PM
            Subject: RE: [William-Optics] Re: Wm-Optics 2" Diagonal


            > That's actually good. The dielectric coatings severely degrade the wave
            > front error in the TV and AP diagonals. While it may make them last longer
            > and makes them brighter, a mirror that starts out as good as 1/25 wave
            will
            > end up around 1/6 or so once the entire dielectric layer stack is layered
            > on. Any small imperfection in the thickness of a layer gets magnified the
            > more layers you put on top of it. I think Vernonscope actually
            experimented
            > with this several years ago and decided against using a dielectric coating
            > because it severely compromised the surface error on the final product.
            And
            > they were using 1/40 wave mirrors also.
            > One reason the TV and AP diagonals appear so good is that they are very
            > careful about aligning the mirrors to be as perfectly on axis as possible.
            > This will make them appear much better than the average one that maybe off
            > slightly. Try setting up a set of optics (SCT/Mak )with as perfect an
            > alignment as you can get with a laser collimator. Then stick every
            diagonal
            > you can get in there with the laser on it and you'd be surprised how many
            > you have access to that may be off alignment (or may have machining errors
            > in the tubes). Even good ones. One of the best aligned diagonals is the
            > Celestron prism diagonal that comes with the scopes. And most guys switch
            to
            > a mirror because it's "better" early on. I've seen so many cases where
            I've
            > had them tell me about problems that I often ask if they still have the
            > original one and then in just about every case I find that the mirror
            > diagonal they replaced it with has an alignment problem. My recommendation
            > is to test every one you are going to buy as even a small alignment error
            > will make the focal plane twisted slightly and reduce performance.
            > Kent Gittings
            >
            > -----Original Message-----
            > From: Ray York [mailto:ray@...]
            > Sent: Thursday, August 09, 2001 1:02 AM
            > To: William-Optics@yahoogroups.com
            > Subject: RE: [William-Optics] Re: Wm-Optics 2" Diagonal
            >
            >
            > Just for clarification, the WO diagonal is NOT dielectrically coated like
            > the TV and AP diagonals are.
            >
            > Ray York
            > Anacortes Telescope and Wild Bird
            > http://www.BuyTelescopes.com/
            > http://www.AstroMart.com/
            > (800) 850-2001
            >
            > -----Original Message-----
            > From: Don Wyman [mailto:dwyman@...]
            > Sent: Wednesday, August 08, 2001 8:35 PM
            > To: William-Optics@yahoogroups.com
            > Subject: [William-Optics] Re: Wm-Optics 2" Diagonal
            >
            > --- In William-Optics@y..., "Dan and Carol" <poziovahim@l...> wrote:
            > > Hey Don! I have the one that came with the Megrez 80 and Its a
            > beaut! I
            > > like the silver side plates rather than the black too! Bueno, Dan
            >
            > Thanks Dan. With all the talk about enhanced mirror diagonals like the
            > TV Everbrite and the AP version, it's nice to see one that doesn't
            > cost an arm and a leg.
            >
            > Don
            >
            >
            >
            > To unsubscribe from this group, send an email to:
            > William-Optics-unsubscribe@yahoogroups.com
            >
            >
            >
            >
            > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
            >
            >
            >
            > To unsubscribe from this group, send an email to:
            > William-Optics-unsubscribe@yahoogroups.com
            >
            >
            >
            >
            > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
            >
            >
            >
            > **********************************************************************
            > This email and any files transmitted with it are confidential and
            > intended solely for the use of the individual or entity to whom they
            > are addressed. If you have received this email in error please notify
            > the system manager.
            >
            > This footnote also confirms that this email message has been swept by
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            > www.mimesweeper.com
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            >
            >
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            >
            >
            >
            >
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            >
            >
          • Kent Gittings
            I was just simplifying it a little Markus. Remember most of the people using this stuff are using the 2 dielectric coated diagonals to use with medium and
            Message 5 of 20 , Aug 10, 2001
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              I was just simplifying it a little Markus. Remember most of the people using
              this stuff are using the 2" dielectric coated diagonals to use with medium
              and high power wide field eyepieces from Nagler, Pentax, etc., so they might
              actually suffer a little.
              Kent Gittings

              -----Original Message-----
              From: Markus Ludes [mailto:apm_telescopes@...]
              Sent: Friday, August 10, 2001 5:39 AM
              To: William-Optics@yahoogroups.com
              Subject: Re: [William-Optics] Re: Wm-Optics 2" Diagonal


              Hi kent,

              your infos are not completed.

              A 99% coating decrease the wave surface area on full surface,it makes an
              high edge, but the center remains perfect, and only the cente ris used by
              high powers.The edge which is not such good is used only by low powers.
              A 96% coating does not decrease at all any of the surface, if right made

              best wishes

              Markus
              ----- Original Message -----
              From: "Kent Gittings" <kent@...>
              To: <William-Optics@yahoogroups.com>
              Sent: Thursday, August 09, 2001 5:10 PM
              Subject: RE: [William-Optics] Re: Wm-Optics 2" Diagonal


              > That's actually good. The dielectric coatings severely degrade the wave
              > front error in the TV and AP diagonals. While it may make them last longer
              > and makes them brighter, a mirror that starts out as good as 1/25 wave
              will
              > end up around 1/6 or so once the entire dielectric layer stack is layered
              > on. Any small imperfection in the thickness of a layer gets magnified the
              > more layers you put on top of it. I think Vernonscope actually
              experimented
              > with this several years ago and decided against using a dielectric coating
              > because it severely compromised the surface error on the final product.
              And
              > they were using 1/40 wave mirrors also.
              > One reason the TV and AP diagonals appear so good is that they are very
              > careful about aligning the mirrors to be as perfectly on axis as possible.
              > This will make them appear much better than the average one that maybe off
              > slightly. Try setting up a set of optics (SCT/Mak )with as perfect an
              > alignment as you can get with a laser collimator. Then stick every
              diagonal
              > you can get in there with the laser on it and you'd be surprised how many
              > you have access to that may be off alignment (or may have machining errors
              > in the tubes). Even good ones. One of the best aligned diagonals is the
              > Celestron prism diagonal that comes with the scopes. And most guys switch
              to
              > a mirror because it's "better" early on. I've seen so many cases where
              I've
              > had them tell me about problems that I often ask if they still have the
              > original one and then in just about every case I find that the mirror
              > diagonal they replaced it with has an alignment problem. My recommendation
              > is to test every one you are going to buy as even a small alignment error
              > will make the focal plane twisted slightly and reduce performance.
              > Kent Gittings
              >
              > -----Original Message-----
              > From: Ray York [mailto:ray@...]
              > Sent: Thursday, August 09, 2001 1:02 AM
              > To: William-Optics@yahoogroups.com
              > Subject: RE: [William-Optics] Re: Wm-Optics 2" Diagonal
              >
              >
              > Just for clarification, the WO diagonal is NOT dielectrically coated like
              > the TV and AP diagonals are.
              >
              > Ray York
              > Anacortes Telescope and Wild Bird
              > http://www.BuyTelescopes.com/
              > http://www.AstroMart.com/
              > (800) 850-2001
              >
              > -----Original Message-----
              > From: Don Wyman [mailto:dwyman@...]
              > Sent: Wednesday, August 08, 2001 8:35 PM
              > To: William-Optics@yahoogroups.com
              > Subject: [William-Optics] Re: Wm-Optics 2" Diagonal
              >
              > --- In William-Optics@y..., "Dan and Carol" <poziovahim@l...> wrote:
              > > Hey Don! I have the one that came with the Megrez 80 and Its a
              > beaut! I
              > > like the silver side plates rather than the black too! Bueno, Dan
              >
              > Thanks Dan. With all the talk about enhanced mirror diagonals like the
              > TV Everbrite and the AP version, it's nice to see one that doesn't
              > cost an arm and a leg.
              >
              > Don
              >
              >
              >
              > To unsubscribe from this group, send an email to:
              > William-Optics-unsubscribe@yahoogroups.com
              >
              >
              >
              >
              > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
              >
              >
              >
              > To unsubscribe from this group, send an email to:
              > William-Optics-unsubscribe@yahoogroups.com
              >
              >
              >
              >
              > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
              >
              >
              >
              > **********************************************************************
              > This email and any files transmitted with it are confidential and
              > intended solely for the use of the individual or entity to whom they
              > are addressed. If you have received this email in error please notify
              > the system manager.
              >
              > This footnote also confirms that this email message has been swept by
              > MIMEsweeper for the presence of computer viruses.
              >
              > www.mimesweeper.com
              > **********************************************************************
              >
              >
              > To unsubscribe from this group, send an email to:
              > William-Optics-unsubscribe@yahoogroups.com
              >
              >
              >
              >
              > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
              >
              >



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              William-Optics-unsubscribe@yahoogroups.com




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              **********************************************************************
              This email and any files transmitted with it are confidential and
              intended solely for the use of the individual or entity to whom they
              are addressed. If you have received this email in error please notify
              the system manager.

              This footnote also confirms that this email message has been swept by
              MIMEsweeper for the presence of computer viruses.

              www.mimesweeper.com
              **********************************************************************
            • dwyman
              Shoot some film? They still make that stuff? . Don
              Message 6 of 20 , Aug 10, 2001
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                Shoot some film? They still make that stuff? <G>.

                Don
              • Moravianus@yahoo.com
                How much could a dielectric diagonal influence the picture if one uses e.g. the new WO 30mm 82 deg. EP with a 102 F7 scope, i.e. a combination of a fast
                Message 7 of 20 , Aug 10, 2001
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                  How much could a dielectric diagonal influence the picture if
                  one uses e.g. the new WO 30mm 82 deg. EP with a 102 F7
                  scope, i.e. a combination of a fast scope, low magnification ?

                  David

                  --- In William-Optics@y..., "Kent Gittings" <kent@i...> wrote:
                  > I was just simplifying it a little Markus. Remember most of the
                  people using
                  > this stuff are using the 2" dielectric coated diagonals to use
                  with medium
                  > and high power wide field eyepieces from Nagler, Pentax, etc.,
                  so they might
                  > actually suffer a little.
                  > Kent Gittings
                  >
                  > -----Original Message-----
                  > From: Markus Ludes [mailto:apm_telescopes@w...]
                  > Sent: Friday, August 10, 2001 5:39 AM
                  > To: William-Optics@y...
                  > Subject: Re: [William-Optics] Re: Wm-Optics 2" Diagonal
                  >
                  >
                  > Hi kent,
                  >
                  > your infos are not completed.
                  >
                  > A 99% coating decrease the wave surface area on full
                  surface,it makes an
                  > high edge, but the center remains perfect, and only the cente
                  ris used by
                  > high powers.The edge which is not such good is used only by
                  low powers.
                  > A 96% coating does not decrease at all any of the surface, if
                  right made
                  >
                  > best wishes
                  >
                  > Markus
                  > ----- Original Message -----
                  > From: "Kent Gittings" <kent@i...>
                  > To: <William-Optics@y...>
                  > Sent: Thursday, August 09, 2001 5:10 PM
                  > Subject: RE: [William-Optics] Re: Wm-Optics 2" Diagonal
                  >
                  >
                  > > That's actually good. The dielectric coatings severely
                  degrade the wave
                  > > front error in the TV and AP diagonals. While it may make
                  them last longer
                  > > and makes them brighter, a mirror that starts out as good as
                  1/25 wave
                  > will
                  > > end up around 1/6 or so once the entire dielectric layer stack
                  is layered
                  > > on. Any small imperfection in the thickness of a layer gets
                  magnified the
                  > > more layers you put on top of it. I think Vernonscope actually
                  > experimented
                  > > with this several years ago and decided against using a
                  dielectric coating
                  > > because it severely compromised the surface error on the
                  final product.
                  > And
                  > > they were using 1/40 wave mirrors also.
                  > > One reason the TV and AP diagonals appear so good is that
                  they are very
                  > > careful about aligning the mirrors to be as perfectly on axis
                  as possible.
                  > > This will make them appear much better than the average
                  one that maybe off
                  > > slightly. Try setting up a set of optics (SCT/Mak )with as
                  perfect an
                  > > alignment as you can get with a laser collimator. Then stick
                  every
                  > diagonal
                  > > you can get in there with the laser on it and you'd be
                  surprised how many
                  > > you have access to that may be off alignment (or may have
                  machining errors
                  > > in the tubes). Even good ones. One of the best aligned
                  diagonals is the
                  > > Celestron prism diagonal that comes with the scopes. And
                  most guys switch
                  > to
                  > > a mirror because it's "better" early on. I've seen so many
                  cases where
                  > I've
                  > > had them tell me about problems that I often ask if they still
                  have the
                  > > original one and then in just about every case I find that the
                  mirror
                  > > diagonal they replaced it with has an alignment problem. My
                  recommendation
                  > > is to test every one you are going to buy as even a small
                  alignment error
                  > > will make the focal plane twisted slightly and reduce
                  performance.
                  > > Kent Gittings
                  > >
                  > > -----Original Message-----
                  > > From: Ray York [mailto:ray@b...]
                  > > Sent: Thursday, August 09, 2001 1:02 AM
                  > > To: William-Optics@y...
                  > > Subject: RE: [William-Optics] Re: Wm-Optics 2" Diagonal
                  > >
                  > >
                  > > Just for clarification, the WO diagonal is NOT dielectrically
                  coated like
                  > > the TV and AP diagonals are.
                  > >
                  > >
                • Dan and Carol
                  The last time I shot any was Ectachrome slide on Halley s comet with my old orange C-8. I had it mounted on one of the first ever GoTo s by Celestron. I think
                  Message 8 of 20 , Aug 10, 2001
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                    The last time I shot any was Ectachrome slide on Halley's comet with my old
                    orange C-8. I had it mounted on one of the first ever GoTo's by Celestron.
                    I think it was called the Genesis w/Great Polaris mount. I had an 11x80
                    finder from University Optics, I think, that set up was sweet. After the
                    great Halley disappointment, I sold it all and got into Radio Control
                    aircraft until 1996. Then I happened to be in a bookstore and just paged
                    thru an Astronomy Magazine and got turned on by all the neat new stuff, sold
                    all my RC stuff and bought the Meade LX 50 10". At least this stuff don't
                    crash and burn and make a grown man weep! Buen cielo, Dan NM
                    -----Original Message-----
                    From: dwyman <dwyman@...>
                    To: William-Optics@yahoogroups.com <William-Optics@yahoogroups.com>
                    Date: Friday, August 10, 2001 7:42 AM
                    Subject: Re: [William-Optics] Re: Wm-Optics 2" Diagonal


                    >Shoot some film? They still make that stuff? <G>.
                    >
                    >Don
                    >
                    >
                    >To unsubscribe from this group, send an email to:
                    >William-Optics-unsubscribe@yahoogroups.com
                    >
                    >
                    >
                    >
                    >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
                    >
                  • Kent Gittings
                    Haven t tried it myself as I have a 152 F9 refractor. I ve played with Brandon 30mm Wide field, Pentax 28mm XL, KK 30mm Wide Scan II and a couple of others
                    Message 9 of 20 , Aug 13, 2001
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                      Haven't tried it myself as I have a 152 F9 refractor. I've played with
                      Brandon 30mm Wide field, Pentax 28mm XL, KK 30mm Wide Scan II and a couple
                      of others using either an Everbright or an Intes 1/15 wave diagonal. With my
                      54 year old eyes I couldn't tell that much difference. Did try it with a
                      0.63x field flattener/focal reducer at F5.7 and with the extra elements in
                      the path the Everbright could have appeared a little brighter but no extra
                      detail was really visible. So I tend to favor highly corrected and aligned
                      diagonals which can be had under $200 instead of higher reflective coatings
                      and possibly lower over all correction. Still mirror alignment in star
                      diagonals appears to be the most common problem I've seen that prevents good
                      observation.
                      Kent Gittings

                      -----Original Message-----
                      From: Moravianus@... [mailto:Moravianus@...]
                      Sent: Friday, August 10, 2001 4:59 PM
                      To: William-Optics@yahoogroups.com
                      Subject: [William-Optics] Re: Dielectric diag. problems was: Wm-Optics
                      2" Diagonal


                      How much could a dielectric diagonal influence the picture if
                      one uses e.g. the new WO 30mm 82 deg. EP with a 102 F7
                      scope, i.e. a combination of a fast scope, low magnification ?

                      David

                      --- In William-Optics@y..., "Kent Gittings" <kent@i...> wrote:
                      > I was just simplifying it a little Markus. Remember most of the
                      people using
                      > this stuff are using the 2" dielectric coated diagonals to use
                      with medium
                      > and high power wide field eyepieces from Nagler, Pentax, etc.,
                      so they might
                      > actually suffer a little.
                      > Kent Gittings
                      >
                      > -----Original Message-----
                      > From: Markus Ludes [mailto:apm_telescopes@w...]
                      > Sent: Friday, August 10, 2001 5:39 AM
                      > To: William-Optics@y...
                      > Subject: Re: [William-Optics] Re: Wm-Optics 2" Diagonal
                      >
                      >
                      > Hi kent,
                      >
                      > your infos are not completed.
                      >
                      > A 99% coating decrease the wave surface area on full
                      surface,it makes an
                      > high edge, but the center remains perfect, and only the cente
                      ris used by
                      > high powers.The edge which is not such good is used only by
                      low powers.
                      > A 96% coating does not decrease at all any of the surface, if
                      right made
                      >
                      > best wishes
                      >
                      > Markus
                      > ----- Original Message -----
                      > From: "Kent Gittings" <kent@i...>
                      > To: <William-Optics@y...>
                      > Sent: Thursday, August 09, 2001 5:10 PM
                      > Subject: RE: [William-Optics] Re: Wm-Optics 2" Diagonal
                      >
                      >
                      > > That's actually good. The dielectric coatings severely
                      degrade the wave
                      > > front error in the TV and AP diagonals. While it may make
                      them last longer
                      > > and makes them brighter, a mirror that starts out as good as
                      1/25 wave
                      > will
                      > > end up around 1/6 or so once the entire dielectric layer stack
                      is layered
                      > > on. Any small imperfection in the thickness of a layer gets
                      magnified the
                      > > more layers you put on top of it. I think Vernonscope actually
                      > experimented
                      > > with this several years ago and decided against using a
                      dielectric coating
                      > > because it severely compromised the surface error on the
                      final product.
                      > And
                      > > they were using 1/40 wave mirrors also.
                      > > One reason the TV and AP diagonals appear so good is that
                      they are very
                      > > careful about aligning the mirrors to be as perfectly on axis
                      as possible.
                      > > This will make them appear much better than the average
                      one that maybe off
                      > > slightly. Try setting up a set of optics (SCT/Mak )with as
                      perfect an
                      > > alignment as you can get with a laser collimator. Then stick
                      every
                      > diagonal
                      > > you can get in there with the laser on it and you'd be
                      surprised how many
                      > > you have access to that may be off alignment (or may have
                      machining errors
                      > > in the tubes). Even good ones. One of the best aligned
                      diagonals is the
                      > > Celestron prism diagonal that comes with the scopes. And
                      most guys switch
                      > to
                      > > a mirror because it's "better" early on. I've seen so many
                      cases where
                      > I've
                      > > had them tell me about problems that I often ask if they still
                      have the
                      > > original one and then in just about every case I find that the
                      mirror
                      > > diagonal they replaced it with has an alignment problem. My
                      recommendation
                      > > is to test every one you are going to buy as even a small
                      alignment error
                      > > will make the focal plane twisted slightly and reduce
                      performance.
                      > > Kent Gittings
                      > >
                      > > -----Original Message-----
                      > > From: Ray York [mailto:ray@b...]
                      > > Sent: Thursday, August 09, 2001 1:02 AM
                      > > To: William-Optics@y...
                      > > Subject: RE: [William-Optics] Re: Wm-Optics 2" Diagonal
                      > >
                      > >
                      > > Just for clarification, the WO diagonal is NOT dielectrically
                      coated like
                      > > the TV and AP diagonals are.
                      > >
                      > >



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