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Re: [ccd-newastro] A fledgling CCD imager who made all the wrong choices...

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  • Lenny Shaffer
    ... As a Nexstar 11 owner I can answer most of your questions I think... *First I would have to say that a second floor porch is NOT the place to start
    Message 1 of 12 , Dec 2, 2003
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      At 10:06 PM 12/2/2003 +0000, you wrote:
      >Here is a sad tale of a new CCD imager who apparantly made all the
      >wrong choices.
      >
      >The recommendations I have heard:
      >
      > "Start with piggyback astrophotography; save prime focus for last as
      >its the hardest"
      > "Use a telescope with a modest focal length and fast optics"
      > "Spend money on the mount, before the scope or camera"
      > "Gadgetry is not the way to go, keep it simple to start"
      > "Polar alignment is king"
      > "Start with black and white...work up to color when you are more
      >experienced."
      > "Whatever you do, don't buy a celestron wedge"
      > "If you want a motorized focuser, don't buy one that moves the
      >primary mirror"
      >
      >In my defense, I came at this unexpectedly from the world of visual
      >observing (in which my setup is rather nice, at least to me). I had
      >no idea I would get hooked on the imaging stuff. At any rate, I have
      >apparantly ignored all the above advice and am trying to learn on the
      >following setup:
      >
      >Nexstar 11 GPS scope (F/10; 2800 mm focal length) ....Ack
      >Scope placed on a celestron wedge in a not-so-stable location (2nd
      >floor porch) where I cannot see Polaris.... Ack
      >SBIG ST7XME camera with CFW8 filter wheel
      >Celestron motofocus attached to the primary focus knob (moves
      >mirror) ..Ack
      >At least I have purchased a focal reducer, so the setup now runs at
      >F/6.5.
      >
      >As you might imagine, despite some patience, I am starting to get
      >frustrated and would appreciate any sage advice from the masters.
      >Even if that advice is dump the whole setup and start with a small
      >refractor on an equitorial mount (don't say that, though, since I do
      >love the scope for visual stuff). I've considered the FASTAR option
      >but I'm concerned that the size of the ST-7 will provide too much of
      >an obstruction. I realize that Starizona makes the C14 hyperstar
      >that will take an ST-7 but that is ~$900, which might be better not
      >spent or spent elsewhere (i.e. on an AO-7 or perhaps hiring someone
      >who knows what they are doing to walk me through this stuff.....)
      >
      >Problem #1: Polar alignment is still atrocious. When I place the
      >scope in a site where I can do a wedge align on polaris, I can get a
      >so-so polar alignment with the drift method. Enough to allow perhaps
      >20 second unguided exposures without trailing. When I move the scope
      >to its primary imaging location (no polaris in sight, southern
      >exposure), things are much worse (8 seconds max). I seem to be
      >having a lot of trouble making adjustments using the drift method.
      >Perhaps I'm just dense but the adjustments on the Celestron wedge do
      >not help things. I wish there was a simple way to reproducibly change
      >the RA on the wedge but that silly little block is about as
      >reproducible as shoving the tripod around. The DEC axis is a bit
      >better, of course. I have tried to take a realistic and patient
      >approach to refining my alignment but I don't seem to be making much
      >progress despite several weeks of effort, reading info on the
      >web,books, etc. Since the adjustments on the wedge are so "shoddy",
      >I end up just moving the tripod around which is, frankly, even less
      >accurate. Clearly, this problem needs to be resolved before I can
      >make any progress with imaging. Any tips, tricks, cheats, or is trial
      >and error the only way to go....
      >
      >Problem #2: Everyone's problem - Focus. I inevitably waste a large
      >amount of time at each imaging session trying to get the scope even
      >close to focus on the CCD. Completely blind. Once I get close, the
      >refinement is no problem using the tools available to me. My
      >motofocus, of course, has no encoders and so this process has to be
      >completely repeated each time (since the scope must be set up and
      >realigned visually each night). Should I just chalk this up to the
      >nature of CCD imaging or buy a motorized or computer controlled
      >focuser that attaches to the visual back (i.e. an NGF-S, or an Optec
      >TCF-S) or a robofocus that attaches to the primary mirror control? I
      >realize that the LAST thing I need is more gadgetry that I can't get
      >to work but focusing the way I currently do seems grossly primitive
      >for all this expensive equipment. Parfocal eyepieces? Seems like a
      >waste of $200 that could be applied to a focuser...but I've been
      >known to make a bad decision in the past...
      >
      >Any advice would be appreciated. Should I just scrap the whole setup
      >and get a small refractor on a decent mount to cut my teeth on?
      >
      >-Rick

      As a Nexstar 11 owner I can answer most of your questions I think...
      *First I would have to say that a second floor porch is NOT the place to
      start attempting imaging.

      *An ST-7 with the filter wheel is a perfectly good starting place.

      *As far as color is concerned I would have to agree that starting with B&W
      is better. Work up to using those color filters.

      *The Celestron heavy duty wedge is NOT adequate for imaging work. If you
      want to spend money then put it into a Mettler, Milburn or soon to be
      released APT wedge rather than a C14 and Hyperstar. There are fixes to help
      eliminate the problems with the wedge posted on several web pages mine
      among them...you need to put locknuts on the AZ adjuster to keep it from
      just unscrewing.

      *Robofocus is the answer to your focusing problems, IMO. You can get
      Focusmax free to automate your focusing under CCDSoft or Maxim/DL. You
      really don't want a focuser that takes up additional back focus distance.
      You'll get into trouble when the scope points toward the zenith.

      *Skip the parfocal eyepieces. If you insist on buying one I'll sell you mine.

      *Start with the f/6.3 reducer corrector and/or buy the f/3.3 reducer
      corrector. Guiding is easier at shorter focal lengths.

      *I've got some pictures up I took with my ST-8XE at
      http://www.intercom.net/user/shaffer/st8_images.html. They aren't the
      greatest but they do show what the Nexstar11 scope and a CCD can do
      together. I've got links to other imagers with the Nexstar.

      *#1 piece of advice?... practice getting your polar alignment setup until
      you have a routine you can go through that maximizes your time with the
      camera. Start with brighter objects and short integrations until you get a
      feel for the camera. Nobody said you can just plot that puppy down and
      image like Rob Gendler. Hang in there....it will all come together one day.



      Lenny

      Your Murphy's Law of the Week:
      "Anything that can go wrong will go wrong."
    • ldbenschop
      Gregg; I don t understand how the AO-7 can compensate for a poor polar alignment. Being a tip-tilt mechanism it has limited range in either direction and with
      Message 2 of 12 , Dec 2, 2003
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        Gregg;
        I don't understand how the AO-7 can compensate for a poor polar
        alignment. Being a tip-tilt mechanism it has limited range in either
        direction and with a poor polar alignment it will end up at one or
        the other travel limits eventually.

        I can see how the AO7 will compensate for moderate Periodic Error,
        and how autoguiding can compensate partially for slightly-off polar
        alignment as well as moderate PE.

        The original message indicated polar alignment only good for 20
        seconds, IMO the only way to compensate for a polar alignment that is
        this far off is to redo the polar alignment.


        --- In ccd-newastro@yahoogroups.com, GREGG KYLE <g.kyle@r...> wrote:
        > If you have to adjust your wedge often because you change
        > locations or move your equipment, get a good wedge. I use
        > the Milburn wedge. There are others that are commonly highly
        > recommended.
        >
        > Also try using PoleAlignMax to automate you polar alignment.
        > Just do a websearch to find the freeware. Not used it myself
        > yet, but it has been given some good reviews.
        >
        > An AO-7 is a nice device for overcoming mount limitations and
        > mediocre polar alignment.
        >
        > Any of the focusers you mentioned are fine. I use Robofocus
        > and TCF-S with equal success.
        >
        > Shopping at AstroMart will help save your pocket book.
        > Particularly for durable items like a wedge, counterweights,
        > etc.
        >
        > Your set up is fine otherwise. It just takes time to get
        > things working and you need a little improvement in your
        > wedge and focuser. Don't give up.
        >
        > Gregg
      • ldbenschop
        Richard; I recommend the following: There really are four areas that are critical as starting points. (1) Learn how to polar align more accurately, should be
        Message 3 of 12 , Dec 2, 2003
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          Richard;
          I recommend the following:

          There really are four areas that are critical as starting points.

          (1) Learn how to polar align more accurately, should be able to image
          for 3-5 minutes without detectable star drift.
          (2)Be sure to know the difference between Periodic Error and drift
          caused by a poor polar alignment.
          (3) Don't train PEC until your polar alignment meets conditions in
          point (1)
          (4) Practise focusing without saving images and once you are
          convinced your focus is good then re-check focus between sub-frames.

          Soliciting the assistance of an experienced person to mentor you will
          shorten the learning curve, but there is still an apprenticeship that
          must be undertaken for any imager.

          Your best assets will be patience and perseverence.

          There are many imagers who are pleased with their work, and part of
          the pleasure comes from the rewards of seeing their work improve over
          time. There are few imagers who don't think they can still do better,
          so although the learning curve will become less steep over time, the
          apprenticeship is a continuing journey.

          Good luck in your journey, it will be worthwhile in the long run!

          Len


          --- In ccd-newastro@yahoogroups.com, "Richard Link" <relink@c...>
          wrote:
          > Here is a sad tale of a new CCD imager who apparantly made all the
          > wrong choices.
          >
          > The recommendations I have heard:
          >
          > "Start with piggyback astrophotography; save prime focus for last
          as
          > its the hardest"
          > "Use a telescope with a modest focal length and fast optics"
          > "Spend money on the mount, before the scope or camera"
          > "Gadgetry is not the way to go, keep it simple to start"
          > "Polar alignment is king"
          > "Start with black and white...work up to color when you are more
          > experienced."
          > "Whatever you do, don't buy a celestron wedge"
          > "If you want a motorized focuser, don't buy one that moves the
          > primary mirror"
          >
          > In my defense, I came at this unexpectedly from the world of visual
          > observing (in which my setup is rather nice, at least to me). I
          had
          > no idea I would get hooked on the imaging stuff. At any rate, I
          have
          > apparantly ignored all the above advice and am trying to learn on
          the
          > following setup:
          >
          > Nexstar 11 GPS scope (F/10; 2800 mm focal length) ....Ack
          > Scope placed on a celestron wedge in a not-so-stable location (2nd
          > floor porch) where I cannot see Polaris.... Ack
          > SBIG ST7XME camera with CFW8 filter wheel
          > Celestron motofocus attached to the primary focus knob (moves
          > mirror) ..Ack
          > At least I have purchased a focal reducer, so the setup now runs at
          > F/6.5.
          >
          > As you might imagine, despite some patience, I am starting to get
          > frustrated and would appreciate any sage advice from the masters.
          > Even if that advice is dump the whole setup and start with a small
          > refractor on an equitorial mount (don't say that, though, since I
          do
          > love the scope for visual stuff). I've considered the FASTAR option
          > but I'm concerned that the size of the ST-7 will provide too much
          of
          > an obstruction. I realize that Starizona makes the C14 hyperstar
          > that will take an ST-7 but that is ~$900, which might be better not
          > spent or spent elsewhere (i.e. on an AO-7 or perhaps hiring someone
          > who knows what they are doing to walk me through this stuff.....)
          >
          > Problem #1: Polar alignment is still atrocious. When I place the
          > scope in a site where I can do a wedge align on polaris, I can get
          a
          > so-so polar alignment with the drift method. Enough to allow
          perhaps
          > 20 second unguided exposures without trailing. When I move the
          scope
          > to its primary imaging location (no polaris in sight, southern
          > exposure), things are much worse (8 seconds max). I seem to be
          > having a lot of trouble making adjustments using the drift method.
          > Perhaps I'm just dense but the adjustments on the Celestron wedge
          do
          > not help things. I wish there was a simple way to reproducibly
          change
          > the RA on the wedge but that silly little block is about as
          > reproducible as shoving the tripod around. The DEC axis is a bit
          > better, of course. I have tried to take a realistic and patient
          > approach to refining my alignment but I don't seem to be making
          much
          > progress despite several weeks of effort, reading info on the
          > web,books, etc. Since the adjustments on the wedge are
          so "shoddy",
          > I end up just moving the tripod around which is, frankly, even less
          > accurate. Clearly, this problem needs to be resolved before I can
          > make any progress with imaging. Any tips, tricks, cheats, or is
          trial
          > and error the only way to go....
          >
          > Problem #2: Everyone's problem - Focus. I inevitably waste a large
          > amount of time at each imaging session trying to get the scope even
          > close to focus on the CCD. Completely blind. Once I get close,
          the
          > refinement is no problem using the tools available to me. My
          > motofocus, of course, has no encoders and so this process has to be
          > completely repeated each time (since the scope must be set up and
          > realigned visually each night). Should I just chalk this up to the
          > nature of CCD imaging or buy a motorized or computer controlled
          > focuser that attaches to the visual back (i.e. an NGF-S, or an
          Optec
          > TCF-S) or a robofocus that attaches to the primary mirror control?
          I
          > realize that the LAST thing I need is more gadgetry that I can't
          get
          > to work but focusing the way I currently do seems grossly primitive
          > for all this expensive equipment. Parfocal eyepieces? Seems like
          a
          > waste of $200 that could be applied to a focuser...but I've been
          > known to make a bad decision in the past...
          >
          > Any advice would be appreciated. Should I just scrap the whole
          setup
          > and get a small refractor on a decent mount to cut my teeth on?
          >
          > -Rick
        • GREGG KYLE
          I agree with you. The AO may not help a polar alignment that is only good for 20 sec. exposures. What I said was it will help with a mediocre alignment . The
          Message 4 of 12 , Dec 2, 2003
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            I agree with you. The AO may not help a polar alignment that
            is only good for 20 sec. exposures.

            What I said was it will help with a "mediocre alignment".
            The AO-7 is able to also bump the mount periodically as the
            guide star drifts. So the adjustment is made through the
            bumps to the mount in both RA and Dec. and does help an
            inexact polar alignment.

            Gregg
          • ldbenschop
            Gregg; I did not realize that the AO7 could also bump the mount, I was under the (false) impression that it could only tip-tilt correct. Thanks, Len
            Message 5 of 12 , Dec 2, 2003
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              Gregg;
              I did not realize that the AO7 could also bump the mount, I was under
              the (false) impression that it could only tip-tilt correct.
              Thanks,
              Len

              --- In ccd-newastro@yahoogroups.com, GREGG KYLE <g.kyle@r...> wrote:
              > I agree with you. The AO may not help a polar alignment that
              > is only good for 20 sec. exposures.
              >
              > What I said was it will help with a "mediocre alignment".
              > The AO-7 is able to also bump the mount periodically as the
              > guide star drifts. So the adjustment is made through the
              > bumps to the mount in both RA and Dec. and does help an
              > inexact polar alignment.
              >
              > Gregg
            • Mike Dodd
              I ll add my relative-newbie opinions to those you ve already read. ... Don t worry about it; use your f/6.5 focal reducer to start, then get an AO-7 if you
              Message 6 of 12 , Dec 2, 2003
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                I'll add my relative-newbie opinions to those you've already read.

                >Nexstar 11 GPS scope (F/10; 2800 mm focal length) ....Ack

                Don't worry about it; use your f/6.5 focal reducer to start, then get an
                AO-7 if you want to image at f/10. Remember, however, the ST-7 has a small
                chip, so you won't get a very wide FOV - some galaxies (e.g., M33) are too
                large for the chip.

                >Scope placed on a celestron wedge in a not-so-stable location (2nd
                >floor porch) where I cannot see Polaris.... Ack

                Get a good wedge like a Mettler or Milburn. Can you find a more stable
                location with, perhaps, concrete pavers to support the tripod feet?

                >SBIG ST7XME camera with CFW8 filter wheel

                A good camera; set aside the color wheel until you master polar alignment,
                focusing, guiding, and exposure. There's a lot to learn.

                >Problem #1: Polar alignment is still atrocious.

                You need a pretty stable setup to achieve and maintain a good polar
                alignment. You're talking about movements in the hundredths of an inch
                range, so you can imagine how difficult that is with a poor wedge and a
                shaky floor.

                >Problem #2: Everyone's problem - Focus. I inevitably waste a large
                >amount of time at each imaging session trying to get the scope even
                >close to focus on the CCD. Completely blind.

                Strange.... I can get a very good focus on the CCD chip in a couple minutes
                just by twisting the focus knob on my 9.25" Celestron SCT. I point the
                scope at a bright star and twist the knob clockwise several turns. I set
                CCDSoft for 1- or 2-second exposures in the Focus Tools tab and twist the
                knob counterclockwise until I see donuts. I have to wait for one complete
                exposure and download after touching the knob, to be sure I got the real
                image. Usually I can get to within about 85%-90% of the focus CCDSoft's
                @Focus can achieve.

                I always finish with @Focus to get a very good focus. BTW, I use the Optec
                TCF-S focuser, and like it a lot.

                I don't think you should scrap your entire setup and start over. First try
                a good wedge and (hopefully) a more stable location. Then see if there's
                any way you can leave the scope set up between sessions; there are various
                semi-weatherproof bags you can use to cover the scope. This will let you
                keep the polar alignment you worked so hard to get, and also leave the
                finder scope attached - and precisely aligned with the center of the CCD
                chip, to make the initial power-up alignment faster.

                Good luck.

                Mike


                ----------
                Mike Dodd
                Montpelier, VA 37N, 77W
                9.25" f/10 Celestron CGE, SBIG ST-7XE
                http://astronomy.mdodd.com
              • Mark de Regt
                Richard, I ll add my voice to what you have heard, mostly agreeing with the consensus. Although I image with an LX200, so I don t know the Nexstar mount well,
                Message 7 of 12 , Dec 2, 2003
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                  Richard,

                  I'll add my voice to what you have heard, mostly agreeing with the
                  consensus.

                  Although I image with an LX200, so I don't know the Nexstar mount well, I
                  suspect that it has shortcomings similar to the LX200. There are ways to
                  compensate.

                  First, you need to image from a solid platform, and that is practically
                  impossible from the second floor of a house. The scope needs to be on
                  something very solid, and that should be isolated from what you are walking
                  on.

                  Get a good wedge; I use the Milburn, and it is very nice.

                  You don't need to see polaris to get a good polar alignment; you just need a
                  proper drift alignment. Here's the bible:
                  http://www.minorplanetobserver.com/htms/Drift_Alignment_Made_Simple.htm It
                  is a pain at first, but becomes second nature quickly. You can shortcut it
                  by noting where your tripod legs are when aligned, and when you set up
                  again, put them in the same place. You should not image until your polar
                  alignment is good enough that you see no drift in a reticle eyepiece for at
                  least five minutes, with stars at the south meridien and at the equator.

                  You should wait on color imaging until you are getting consistently good
                  results in grayscale. This hobby is about mastering a whole bunch of
                  processes, none of which is very difficult by itself, but which can be
                  overwhelming if taken on all at once.

                  Use a .33 reducer; it will ease the problems with your mount. Unless your
                  mount is horrible, which it probably is not, you should be able to get
                  decent to good results that way. About half the pictures on my website were
                  taken with a .33 reducer with an ST-7E with my LX200.

                  The AO-7 is the magic bullet for sloppier mounts, but don't get one until
                  you have mastered imaging at a shorter focal length; it's just one more
                  complication, which is not difficult at the right time but will be baffling
                  now.

                  Focusing is the single hardest thing in imaging. Use the hartman mask
                  method Ron talks about in his book; if money is an issue, get an NGF-S; if
                  money is not an issue, get a TCF-S. Focus is a pain, but doable.
                  Eventually, you will want to get a Robofocus or other precise focus motor,
                  so you can focus automatically, but you don't have to start out that way.
                  Don't get parfocal eyepieces; learning to do it right is worth the effort.
                  When I started, it sometimes took me an hour to focus. Now, I can focus in
                  a very few minutes, even without the automatic focus routine.

                  Use a good camera control software, like CCDSoft, and use a good planetarium
                  program, like TheSky.

                  You should not scrap your setup. You should be able to do some nice work
                  with it. Later on, you might want to buy better equipment if you have the
                  bucks, but buying the fanciest equipment in the world would make very little
                  difference to you right now--there's just a lot to learn, whatever your
                  equipment.

                  This hobby is very expensive, even without buying $15,000 optical tubes.

                  This is also an immensely frustrating hobby, but (at least to me) worth the
                  problems. I think it pretty neat that, even at the start, you can take a
                  recognizable (if primitive) image, but that you keep getting better for
                  years. It has not gotten boring!

                  Keep at it, and ask any questions you want here.

                  Mark de Regt
                  Redmond, Washington, USA
                  47.7 N. Latitude; 122 West Longitude
                  Astro Images: http://home.earthlink.net/~akilla/MAD




                  > -----Original Message-----
                  > From: Richard Link [mailto:relink@...]
                  > Sent: Tuesday, December 02, 2003 2:07 PM
                  > To: ccd-newastro@yahoogroups.com
                  > Subject: [ccd-newastro] A fledgling CCD imager who made all the wrong
                  > choices...
                  >
                  >
                  > Here is a sad tale of a new CCD imager who apparantly made all the
                  > wrong choices.
                  >
                  > The recommendations I have heard:
                  >
                  > "Start with piggyback astrophotography; save prime focus for last as
                  > its the hardest"
                  > "Use a telescope with a modest focal length and fast optics"
                  > "Spend money on the mount, before the scope or camera"
                  > "Gadgetry is not the way to go, keep it simple to start"
                  > "Polar alignment is king"
                  > "Start with black and white...work up to color when you are more
                  > experienced."
                  > "Whatever you do, don't buy a celestron wedge"
                  > "If you want a motorized focuser, don't buy one that moves the
                  > primary mirror"
                  >
                  > In my defense, I came at this unexpectedly from the world of visual
                  > observing (in which my setup is rather nice, at least to me). I had
                  > no idea I would get hooked on the imaging stuff. At any rate, I have
                  > apparantly ignored all the above advice and am trying to learn on the
                  > following setup:
                  >
                  > Nexstar 11 GPS scope (F/10; 2800 mm focal length) ....Ack
                  > Scope placed on a celestron wedge in a not-so-stable location (2nd
                  > floor porch) where I cannot see Polaris.... Ack
                  > SBIG ST7XME camera with CFW8 filter wheel
                  > Celestron motofocus attached to the primary focus knob (moves
                  > mirror) ..Ack
                  > At least I have purchased a focal reducer, so the setup now runs at
                  > F/6.5.
                  >
                  > As you might imagine, despite some patience, I am starting to get
                  > frustrated and would appreciate any sage advice from the masters.
                  > Even if that advice is dump the whole setup and start with a small
                  > refractor on an equitorial mount (don't say that, though, since I do
                  > love the scope for visual stuff). I've considered the FASTAR option
                  > but I'm concerned that the size of the ST-7 will provide too much of
                  > an obstruction. I realize that Starizona makes the C14 hyperstar
                  > that will take an ST-7 but that is ~$900, which might be better not
                  > spent or spent elsewhere (i.e. on an AO-7 or perhaps hiring someone
                  > who knows what they are doing to walk me through this stuff.....)
                  >
                  > Problem #1: Polar alignment is still atrocious. When I place the
                  > scope in a site where I can do a wedge align on polaris, I can get a
                  > so-so polar alignment with the drift method. Enough to allow perhaps
                  > 20 second unguided exposures without trailing. When I move the scope
                  > to its primary imaging location (no polaris in sight, southern
                  > exposure), things are much worse (8 seconds max). I seem to be
                  > having a lot of trouble making adjustments using the drift method.
                  > Perhaps I'm just dense but the adjustments on the Celestron wedge do
                  > not help things. I wish there was a simple way to reproducibly change
                  > the RA on the wedge but that silly little block is about as
                  > reproducible as shoving the tripod around. The DEC axis is a bit
                  > better, of course. I have tried to take a realistic and patient
                  > approach to refining my alignment but I don't seem to be making much
                  > progress despite several weeks of effort, reading info on the
                  > web,books, etc. Since the adjustments on the wedge are so "shoddy",
                  > I end up just moving the tripod around which is, frankly, even less
                  > accurate. Clearly, this problem needs to be resolved before I can
                  > make any progress with imaging. Any tips, tricks, cheats, or is trial
                  > and error the only way to go....
                  >
                  > Problem #2: Everyone's problem - Focus. I inevitably waste a large
                  > amount of time at each imaging session trying to get the scope even
                  > close to focus on the CCD. Completely blind. Once I get close, the
                  > refinement is no problem using the tools available to me. My
                  > motofocus, of course, has no encoders and so this process has to be
                  > completely repeated each time (since the scope must be set up and
                  > realigned visually each night). Should I just chalk this up to the
                  > nature of CCD imaging or buy a motorized or computer controlled
                  > focuser that attaches to the visual back (i.e. an NGF-S, or an Optec
                  > TCF-S) or a robofocus that attaches to the primary mirror control? I
                  > realize that the LAST thing I need is more gadgetry that I can't get
                  > to work but focusing the way I currently do seems grossly primitive
                  > for all this expensive equipment. Parfocal eyepieces? Seems like a
                  > waste of $200 that could be applied to a focuser...but I've been
                  > known to make a bad decision in the past...
                  >
                  > Any advice would be appreciated. Should I just scrap the whole setup
                  > and get a small refractor on a decent mount to cut my teeth on?
                  >
                  > -Rick
                  >
                  >
                  >
                  >
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                  > ccd-newastro-unsubscribe@egroups.com
                  >
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                  >
                  >
                • Tim Long
                  You are correct, there is no substitute for good polar alignment. To some extent, guiding can correct for poor alignment (but not for field rotation). The AO-7
                  Message 8 of 12 , Dec 2, 2003
                  • 0 Attachment
                    You are correct, there is no substitute for good polar alignment. To
                    some extent, guiding can correct for poor alignment (but not for field
                    rotation). The AO-7 works in conjunction with the normal autoguiding
                    mechanism to keep the guide star centered. When the AO-7 deflection
                    reaches a certain threshold, the mount is "bumped" using the guider
                    port. Because the AO-7 has a fast response time, it can compensate for
                    the mount movement during the "bump".

                    It isn't a complete cure for a bad mount, but it is a very big step in
                    the right direction.

                    --Tim

                    > -----Original Message-----
                    > From: ldbenschop [mailto:lbenschop@...]
                    > Sent: Wednesday 3 December 2003 00:04
                    > To: ccd-newastro@yahoogroups.com
                    > Subject: [ccd-newastro] Re: A fledgling CCD imager who made
                    > all the wrong choices...
                    >
                    > Gregg;
                    > I don't understand how the AO-7 can compensate for a poor
                    > polar alignment. Being a tip-tilt mechanism it has limited
                    > range in either direction and with a poor polar alignment it
                    > will end up at one or the other travel limits eventually.
                    >
                    > I can see how the AO7 will compensate for moderate Periodic
                    > Error, and how autoguiding can compensate partially for
                    > slightly-off polar alignment as well as moderate PE.
                    >
                    > The original message indicated polar alignment only good for
                    > 20 seconds, IMO the only way to compensate for a polar
                    > alignment that is this far off is to redo the polar alignment.
                    >
                    >
                    > --- In ccd-newastro@yahoogroups.com, GREGG KYLE <g.kyle@r...> wrote:
                    > > If you have to adjust your wedge often because you change
                    > locations or
                    > > move your equipment, get a good wedge. I use the Milburn wedge.
                    > > There are others that are commonly highly recommended.
                    > >
                    > > Also try using PoleAlignMax to automate you polar alignment.
                    > > Just do a websearch to find the freeware. Not used it
                    > myself yet, but
                    > > it has been given some good reviews.
                    > >
                    > > An AO-7 is a nice device for overcoming mount limitations
                    > and mediocre
                    > > polar alignment.
                    > >
                    > > Any of the focusers you mentioned are fine. I use
                    > Robofocus and TCF-S
                    > > with equal success.
                    > >
                    > > Shopping at AstroMart will help save your pocket book.
                    > > Particularly for durable items like a wedge, counterweights, etc.
                    > >
                    > > Your set up is fine otherwise. It just takes time to get things
                    > > working and you need a little improvement in your wedge and
                    > focuser.
                    > > Don't give up.
                    > >
                    > > Gregg
                    >
                    >
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                  • ldbenschop
                    Tim; Thanks - Didn t realize at the time I posted that the AO-7 could also bump the mount! Cool stuff! Len ... field ... for ... in ... wedge. ... etc. ...
                    Message 9 of 12 , Dec 3, 2003
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                      Tim;
                      Thanks - Didn't realize at the time I posted that the AO-7 could also
                      bump the mount!
                      Cool stuff!

                      Len

                      --- In ccd-newastro@yahoogroups.com, "Tim Long" <Tim@l...> wrote:
                      > You are correct, there is no substitute for good polar alignment. To
                      > some extent, guiding can correct for poor alignment (but not for
                      field
                      > rotation). The AO-7 works in conjunction with the normal autoguiding
                      > mechanism to keep the guide star centered. When the AO-7 deflection
                      > reaches a certain threshold, the mount is "bumped" using the guider
                      > port. Because the AO-7 has a fast response time, it can compensate
                      for
                      > the mount movement during the "bump".
                      >
                      > It isn't a complete cure for a bad mount, but it is a very big step
                      in
                      > the right direction.
                      >
                      > --Tim
                      >
                      > > -----Original Message-----
                      > > From: ldbenschop [mailto:lbenschop@h...]
                      > > Sent: Wednesday 3 December 2003 00:04
                      > > To: ccd-newastro@yahoogroups.com
                      > > Subject: [ccd-newastro] Re: A fledgling CCD imager who made
                      > > all the wrong choices...
                      > >
                      > > Gregg;
                      > > I don't understand how the AO-7 can compensate for a poor
                      > > polar alignment. Being a tip-tilt mechanism it has limited
                      > > range in either direction and with a poor polar alignment it
                      > > will end up at one or the other travel limits eventually.
                      > >
                      > > I can see how the AO7 will compensate for moderate Periodic
                      > > Error, and how autoguiding can compensate partially for
                      > > slightly-off polar alignment as well as moderate PE.
                      > >
                      > > The original message indicated polar alignment only good for
                      > > 20 seconds, IMO the only way to compensate for a polar
                      > > alignment that is this far off is to redo the polar alignment.
                      > >
                      > >
                      > > --- In ccd-newastro@yahoogroups.com, GREGG KYLE <g.kyle@r...>
                      wrote:
                      > > > If you have to adjust your wedge often because you change
                      > > locations or
                      > > > move your equipment, get a good wedge. I use the Milburn
                      wedge.
                      > > > There are others that are commonly highly recommended.
                      > > >
                      > > > Also try using PoleAlignMax to automate you polar alignment.
                      > > > Just do a websearch to find the freeware. Not used it
                      > > myself yet, but
                      > > > it has been given some good reviews.
                      > > >
                      > > > An AO-7 is a nice device for overcoming mount limitations
                      > > and mediocre
                      > > > polar alignment.
                      > > >
                      > > > Any of the focusers you mentioned are fine. I use
                      > > Robofocus and TCF-S
                      > > > with equal success.
                      > > >
                      > > > Shopping at AstroMart will help save your pocket book.
                      > > > Particularly for durable items like a wedge, counterweights,
                      etc.
                      > > >
                      > > > Your set up is fine otherwise. It just takes time to get
                      things
                      > > > working and you need a little improvement in your wedge and
                      > > focuser.
                      > > > Don't give up.
                      > > >
                      > > > Gregg
                      > >
                      > >
                      > > ------------------------ Yahoo! Groups Sponsor
                      > > ---------------------~--> Buy Ink Cartridges or Refill Kits
                      > > for your HP, Epson, Canon or Lexmark Printer at MyInks.com.
                      > > Free s/h on orders $50 or more to the US & Canada.
                      > > http://www.c1tracking.com/l.asp?cid=5511
                      > > http://us.click.yahoo.com/mOAaAA/3exGAA/qnsNAA/N_XolB/TM
                      > > --------------------------------------------------------------
                      > > -------~->
                      > >
                      > > 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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