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Re: [ccd-newastro] Need focal reducer help!

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  • RONALD BRANT
    AO-7 will work with f/6.3, not f/3.3. At least I haven t found a way! Ron B. ... From: uwpf23 To: ccd-newastro@yahoogroups.com Sent: Sunday, November 30, 2003
    Message 1 of 9 , Nov 30, 2003
      AO-7 will work with f/6.3, not f/3.3. At least I haven't found a way!
      Ron B.


      ----- Original Message -----
      From: uwpf23
      To: ccd-newastro@yahoogroups.com
      Sent: Sunday, November 30, 2003 8:29 PM
      Subject: [ccd-newastro] Need focal reducer help!


      Hi,
      I cannot achieve focus with a Meade F/3.3 focal reducer used with
      the following:
      1) Celestron CGE-1400 OTA. 3910mm focal length @ F-11 when no focal
      reducer used.
      2) CCD setup is an ST-7/CFW-8/AO-7 all attached together.
      3) JMI SmartFocus elecric micro-focuser.

      I've tried the following already:
      1) Mounted the reducer directly onto the visual back of the OTA first,
      then attached the JMI, then the CCD gear. Racked the Celestron
      main focus knob all the way clockwise (mirror moved all the way
      back toward the rear). The image was moving toward focus, but
      could not get all the way focused.
      2) Mounted JMI focuser first, then the reducer, then the CCD gear.
      Same result.

      Note: I CAN get focus with the F/3.3 reducer through the eyepiece and
      a star diagonal visually (NO CCD attached).

      Is my problem that the focal reducer lens is too far away from the
      CCD chip with all the gear attached? Or, is it too close to the CCD
      chip? It seems from the visual eyepiece check that the reducer is
      too far away from the CCD chip. I can't get it any closer without
      removing some of the CCD attachments, which is not feasible for me
      (can't do without the color wheel or adaptive optics).

      Anybody have any ideas on what the cure for this is? If this specific
      focal reducer is incompatible, anybody have any suggestions for brands
      that will work and are faster than F/6.3 (already have a .63 from
      Celestron that works fine--just need shorter focal lengths than this
      with such a long main focal length to work with!). Would like to get
      down to at least F/4 or 4.5 if possible, as F/6.3 just is not
      desirable with some objects on the CGE-1400.

      Thanks for any help you all can give me on this!

      Clear skies,
      Wade Van Arsdale
      Little Rock, AR.
      (Registered NewAstro Customer)



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    • Jim Thibert
      I have found with all the ccd optical train, especially when using a c14and st7 that .63 is tough enough let alone 3.3 R/C For the .63, I went to a VSE focuser
      Message 2 of 9 , Dec 1, 2003
        I have found with all the ccd optical train, especially when using a c14and
        st7 that .63 is tough enough let alone 3.3 R/C

        For the .63, I went to a VSE focuser where the R/C is zero offset because
        its inside



        Good skies-clear eyes

        JImmy
        http://www.forterieobservatory.com
        formerly, www.frenchriverobservatory.com

        W78-55-12 N42-54-25
        C-14@f5.1 (st7-i/cfw8)and TV101(st7-e) on ParamountME with VSE m-3Robo





        ----Original Message Follows----
        From: "uwpf23" <uwpf23@...>
        Reply-To: ccd-newastro@yahoogroups.com
        To: ccd-newastro@yahoogroups.com
        Subject: [ccd-newastro] Need focal reducer help!
        Date: Mon, 01 Dec 2003 04:29:25 -0000

        Hi,
        I cannot achieve focus with a Meade F/3.3 focal reducer used with
        the following:
        1) Celestron CGE-1400 OTA. 3910mm focal length @ F-11 when no focal
        reducer used.
        2) CCD setup is an ST-7/CFW-8/AO-7 all attached together.
        3) JMI SmartFocus elecric micro-focuser.

        I've tried the following already:
        1) Mounted the reducer directly onto the visual back of the OTA first,
        then attached the JMI, then the CCD gear. Racked the Celestron
        main focus knob all the way clockwise (mirror moved all the way
        back toward the rear). The image was moving toward focus, but
        could not get all the way focused.
        2) Mounted JMI focuser first, then the reducer, then the CCD gear.
        Same result.

        Note: I CAN get focus with the F/3.3 reducer through the eyepiece and
        a star diagonal visually (NO CCD attached).

        Is my problem that the focal reducer lens is too far away from the
        CCD chip with all the gear attached? Or, is it too close to the CCD
        chip? It seems from the visual eyepiece check that the reducer is
        too far away from the CCD chip. I can't get it any closer without
        removing some of the CCD attachments, which is not feasible for me
        (can't do without the color wheel or adaptive optics).

        Anybody have any ideas on what the cure for this is? If this specific
        focal reducer is incompatible, anybody have any suggestions for brands
        that will work and are faster than F/6.3 (already have a .63 from
        Celestron that works fine--just need shorter focal lengths than this
        with such a long main focal length to work with!). Would like to get
        down to at least F/4 or 4.5 if possible, as F/6.3 just is not
        desirable with some objects on the CGE-1400.

        Thanks for any help you all can give me on this!

        Clear skies,
        Wade Van Arsdale
        Little Rock, AR.
        (Registered NewAstro Customer)




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



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      • Roger Hamlett
        ... Too far from the CCD chip. ... You will allready be using a compressor that is more extreme than F*.63. The reduction acheived by a compressor, is
        Message 3 of 9 , Dec 1, 2003
          > Hi,
          > I cannot achieve focus with a Meade F/3.3 focal reducer used with
          > the following:
          > 1) Celestron CGE-1400 OTA. 3910mm focal length @ F-11 when no focal
          > reducer used.
          > 2) CCD setup is an ST-7/CFW-8/AO-7 all attached together.
          > 3) JMI SmartFocus elecric micro-focuser.
          >
          > I've tried the following already:
          > 1) Mounted the reducer directly onto the visual back of the OTA first,
          > then attached the JMI, then the CCD gear. Racked the Celestron
          > main focus knob all the way clockwise (mirror moved all the way
          > back toward the rear). The image was moving toward focus, but
          > could not get all the way focused.
          > 2) Mounted JMI focuser first, then the reducer, then the CCD gear.
          > Same result.
          >
          > Note: I CAN get focus with the F/3.3 reducer through the eyepiece and
          > a star diagonal visually (NO CCD attached).
          >
          > Is my problem that the focal reducer lens is too far away from the
          > CCD chip with all the gear attached? Or, is it too close to the CCD
          > chip? It seems from the visual eyepiece check that the reducer is
          > too far away from the CCD chip. I can't get it any closer without
          > removing some of the CCD attachments, which is not feasible for me
          > (can't do without the color wheel or adaptive optics).
          Too far from the CCD chip.

          > Anybody have any ideas on what the cure for this is? If this specific
          > focal reducer is incompatible, anybody have any suggestions for brands
          > that will work and are faster than F/6.3 (already have a .63 from
          > Celestron that works fine--just need shorter focal lengths than this
          > with such a long main focal length to work with!). Would like to get
          > down to at least F/4 or 4.5 if possible, as F/6.3 just is not
          > desirable with some objects on the CGE-1400.
          >
          > Thanks for any help you all can give me on this!
          You will allready be using a compressor that is more extreme than F*.63. The
          reduction acheived by a compressor, is dependant on it's own focal length,
          and the distance to the target. Assuming you have the F*.63, mounted with
          the normal "captain's wheel" on the AO7, the compressor will be running at
          about F*.5. The final focal ratio achieved though, is dependant on the scope
          itself. As the back focus increases (which with the compressor and the
          distances involved with the focusser, will be at perhaps 300mm), the scope
          itself give higher than design focal ratios. It's design ratio is F/11, and
          with the extended backfocus, it will probably be working more like F/12.5,
          giving you a final ratio close to F/6.3. You will not get much more extreme
          than the ratio you are allready using, without severe problems elsewhere
          (you will be getting some shading of the main CCD, by the 'pick off' for the
          guide CCD, vignetting from the filters and compressor etc. etc..).
          The 'key' of the AO7, is that it allows detailed imaging at quite long focal
          lengths, by giving fast accurate guiding. You have two basic choices:
          1) Stick with the high focal ratio, and use the AO7.
          2) Remove the AO7 and image at perhaps F/4 (which should be fine with normal
          guiding).
          You _can_ 'do without' the adaptive optics, when running at shorter focal
          lengths.

          Best Wishes
        • uwpf23
          Hi Roger, Thanks very much for your help on this. That is the same thing that I (being a CCD novice) had concluded--too far away from the CCD chip. I m
          Message 4 of 9 , Dec 1, 2003
            Hi Roger,
            Thanks very much for your help on this. That is the same thing that
            I (being a CCD novice) had concluded--too far away from the CCD chip.
            I'm considering one other option--I have a Celestron ST-80 F/5
            refractor mounted on the main 14 inch OTA. If I can find the proper
            T-Ring to adapt it's focuser tube to the captain's wheel of the AO-7,
            (even though the AO-7 wouldn't be needed here--just don't want to
            mess with taking it apart every time!), I will try imaging and
            manually focusing with an aperature mask through the ST-80 for the
            very large sky objects (M42, etc...), then just go with the setup you
            recommended below for the fainter, smaller objects. I may wind up
            having a similar distance problem with the ST-80 though, even without
            the reducer and JMI focuser: focus may be too far away from the CCD
            chip to rack the drawtube in far enough to get there. I may not have
            any other choice but to take the AO-7 off when using the refractor.
            Any comments on this setup with the ST-80 refractor would be greatly
            appreciated, as well.

            Thanks also for the information on the 14 inch OTA F-values with the
            .63 compressor. This will aid greatly in fine-tuning the proper
            binning mode to get a more reasonable arc-sec/pixel value with such
            long focal lengths! Looks like I'll be using 3x3 binning most of the
            time with this long focal length.

            Clear skies,
            Wade Van Arsdale

            //////////////////////////////////////////////////////////////////




            --- In ccd-newastro@yahoogroups.com, "Roger Hamlett" <roger@t...>
            wrote:
            > > Hi,
            > > I cannot achieve focus with a Meade F/3.3 focal reducer used with
            > > the following:
            > > 1) Celestron CGE-1400 OTA. 3910mm focal length @ F-11 when no
            focal
            > > reducer used.
            > > 2) CCD setup is an ST-7/CFW-8/AO-7 all attached together.
            > > 3) JMI SmartFocus elecric micro-focuser.
            > >
            > > I've tried the following already:
            > > 1) Mounted the reducer directly onto the visual back of the OTA
            first,
            > > then attached the JMI, then the CCD gear. Racked the Celestron
            > > main focus knob all the way clockwise (mirror moved all the way
            > > back toward the rear). The image was moving toward focus, but
            > > could not get all the way focused.
            > > 2) Mounted JMI focuser first, then the reducer, then the CCD gear.
            > > Same result.
            > >
            > > Note: I CAN get focus with the F/3.3 reducer through the eyepiece
            and
            > > a star diagonal visually (NO CCD attached).
            > >
            > > Is my problem that the focal reducer lens is too far away from the
            > > CCD chip with all the gear attached? Or, is it too close to the
            CCD
            > > chip? It seems from the visual eyepiece check that the reducer is
            > > too far away from the CCD chip. I can't get it any closer without
            > > removing some of the CCD attachments, which is not feasible for me
            > > (can't do without the color wheel or adaptive optics).
            > Too far from the CCD chip.
            >
            > > Anybody have any ideas on what the cure for this is? If this
            specific
            > > focal reducer is incompatible, anybody have any suggestions for
            brands
            > > that will work and are faster than F/6.3 (already have a .63 from
            > > Celestron that works fine--just need shorter focal lengths than
            this
            > > with such a long main focal length to work with!). Would like to
            get
            > > down to at least F/4 or 4.5 if possible, as F/6.3 just is not
            > > desirable with some objects on the CGE-1400.
            > >
            > > Thanks for any help you all can give me on this!
            > You will allready be using a compressor that is more extreme than
            F*.63. The
            > reduction acheived by a compressor, is dependant on it's own focal
            length,
            > and the distance to the target. Assuming you have the F*.63,
            mounted with
            > the normal "captain's wheel" on the AO7, the compressor will be
            running at
            > about F*.5. The final focal ratio achieved though, is dependant on
            the scope
            > itself. As the back focus increases (which with the compressor and
            the
            > distances involved with the focusser, will be at perhaps 300mm),
            the scope
            > itself give higher than design focal ratios. It's design ratio is
            F/11, and
            > with the extended backfocus, it will probably be working more like
            F/12.5,
            > giving you a final ratio close to F/6.3. You will not get much more
            extreme
            > than the ratio you are allready using, without severe problems
            elsewhere
            > (you will be getting some shading of the main CCD, by the 'pick
            off' for the
            > guide CCD, vignetting from the filters and compressor etc. etc..).
            > The 'key' of the AO7, is that it allows detailed imaging at quite
            long focal
            > lengths, by giving fast accurate guiding. You have two basic
            choices:
            > 1) Stick with the high focal ratio, and use the AO7.
            > 2) Remove the AO7 and image at perhaps F/4 (which should be fine
            with normal
            > guiding).
            > You _can_ 'do without' the adaptive optics, when running at shorter
            focal
            > lengths.
            >
            > Best Wishes
          • Roger Hamlett
            ... You are obviously interested in going for quite wide fields . At least with the ST7, you won t get microlens artefacts, (which can get quite bad on the
            Message 5 of 9 , Dec 2, 2003
              > Hi Roger,
              > Thanks very much for your help on this. That is the same thing that
              > I (being a CCD novice) had concluded--too far away from the CCD chip.
              > I'm considering one other option--I have a Celestron ST-80 F/5
              > refractor mounted on the main 14 inch OTA. If I can find the proper
              > T-Ring to adapt it's focuser tube to the captain's wheel of the AO-7,
              > (even though the AO-7 wouldn't be needed here--just don't want to
              > mess with taking it apart every time!), I will try imaging and
              > manually focusing with an aperature mask through the ST-80 for the
              > very large sky objects (M42, etc...), then just go with the setup you
              > recommended below for the fainter, smaller objects. I may wind up
              > having a similar distance problem with the ST-80 though, even without
              > the reducer and JMI focuser: focus may be too far away from the CCD
              > chip to rack the drawtube in far enough to get there. I may not have
              > any other choice but to take the AO-7 off when using the refractor.
              > Any comments on this setup with the ST-80 refractor would be greatly
              > appreciated, as well.
              You are obviously interested in going for quite 'wide fields'. At least with
              the ST7, you won't get 'microlens' artefacts, (which can get quite bad on
              the lensed CCD's at fast focal ratios). :-)

              > Thanks also for the information on the 14 inch OTA F-values with the
              > .63 compressor. This will aid greatly in fine-tuning the proper
              > binning mode to get a more reasonable arc-sec/pixel value with such
              > long focal lengths! Looks like I'll be using 3x3 binning most of the
              > time with this long focal length.
              I'd have expected the compressor to be showing some noticable aberrations at
              the large spacing. The 'design' spacing, is about 90mm from the base of the
              threads, to the CCD (to give 0.63*). The AO7 body itself adds nearly this
              much, while the colour wheel, distance to CCD inside the camera body, and
              the long front port on the AO7, all extend this distance. Generally, to get
              reasonably good images, to the edge of the field with the compressor and the
              AO7, it is necessary to reduce this distance as much as possible. Hence the
              adapter here:
              http://www.ziplink.net/~lester/FLR.html
              Though this will reduce the focal compression you get from the existing
              unit, the scopes focal ratio will drop a little, and the overall field will
              not be that different, but the quality across the field will be better.
              For really wide fields, a shorter focal length scope will be the answer.
              However remember you can allways take a sequence of images binned 3*3 (say),
              and make a mosaic.
              Once you get the suitable adapter to try this, rain will be guaranteed for a
              few weeks... (personal depressing forecast).

              Best Wishes
            • uwpf23
              Thanks for the info Jim! Clear skies, Wade ... a c14and ... because ... 3Robo ... first, ... and ... CCD ... specific ... brands ... this ... get ...
              Message 6 of 9 , Dec 2, 2003
                Thanks for the info Jim!

                Clear skies,
                Wade

                ////////////////////////////////////////////////////////////////
                --- In ccd-newastro@yahoogroups.com, "Jim Thibert" <thibertj@h...>
                wrote:
                > I have found with all the ccd optical train, especially when using
                a c14and
                > st7 that .63 is tough enough let alone 3.3 R/C
                >
                > For the .63, I went to a VSE focuser where the R/C is zero offset
                because
                > its inside
                >
                >
                >
                > Good skies-clear eyes
                >
                > JImmy
                > http://www.forterieobservatory.com
                > formerly, www.frenchriverobservatory.com
                >
                > W78-55-12 N42-54-25
                > C-14@f... (st7-i/cfw8)and TV101(st7-e) on ParamountME with VSE m-
                3Robo
                >
                >
                >
                >
                >
                > ----Original Message Follows----
                > From: "uwpf23" <uwpf23@y...>
                > Reply-To: ccd-newastro@yahoogroups.com
                > To: ccd-newastro@yahoogroups.com
                > Subject: [ccd-newastro] Need focal reducer help!
                > Date: Mon, 01 Dec 2003 04:29:25 -0000
                >
                > Hi,
                > I cannot achieve focus with a Meade F/3.3 focal reducer used with
                > the following:
                > 1) Celestron CGE-1400 OTA. 3910mm focal length @ F-11 when no focal
                > reducer used.
                > 2) CCD setup is an ST-7/CFW-8/AO-7 all attached together.
                > 3) JMI SmartFocus elecric micro-focuser.
                >
                > I've tried the following already:
                > 1) Mounted the reducer directly onto the visual back of the OTA
                first,
                > then attached the JMI, then the CCD gear. Racked the Celestron
                > main focus knob all the way clockwise (mirror moved all the way
                > back toward the rear). The image was moving toward focus, but
                > could not get all the way focused.
                > 2) Mounted JMI focuser first, then the reducer, then the CCD gear.
                > Same result.
                >
                > Note: I CAN get focus with the F/3.3 reducer through the eyepiece
                and
                > a star diagonal visually (NO CCD attached).
                >
                > Is my problem that the focal reducer lens is too far away from the
                > CCD chip with all the gear attached? Or, is it too close to the
                CCD
                > chip? It seems from the visual eyepiece check that the reducer is
                > too far away from the CCD chip. I can't get it any closer without
                > removing some of the CCD attachments, which is not feasible for me
                > (can't do without the color wheel or adaptive optics).
                >
                > Anybody have any ideas on what the cure for this is? If this
                specific
                > focal reducer is incompatible, anybody have any suggestions for
                brands
                > that will work and are faster than F/6.3 (already have a .63 from
                > Celestron that works fine--just need shorter focal lengths than
                this
                > with such a long main focal length to work with!). Would like to
                get
                > down to at least F/4 or 4.5 if possible, as F/6.3 just is not
                > desirable with some objects on the CGE-1400.
                >
                > Thanks for any help you all can give me on this!
                >
                > Clear skies,
                > Wade Van Arsdale
                > Little Rock, AR.
                > (Registered NewAstro Customer)
                >
                >
                >
                >
                > 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/
                >
                > _________________________________________________________________
                > Add photos to your e-mail with MSN 8. Get 2 months FREE*.
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                3den-ca
              • uwpf23
                Thanks Mark. I think I m going to use a Celestron ST80 guide scope mounted piggyback for the larger objects (with the AO-7 removed), and use the .63
                Message 7 of 9 , Dec 2, 2003
                  Thanks Mark. I think I'm going to use a Celestron ST80 guide
                  scope mounted piggyback for the larger objects (with the AO-7
                  removed), and use the .63 reducer/AO-7 with the C-14 the rest of the
                  time. Appreciate the help from everybody who responded!

                  Clear skies,
                  Wade
                  ///////////////////////////////////////////////////////////////////

                  --- In ccd-newastro@yahoogroups.com, "Mark de Regt" <deregt@e...>
                  wrote:
                  > You can't use a Meade .33 reducer with the AO-7--the distance is
                  too great
                  > from reducer to chip, and you won't be able to focus (even if you
                  could, the
                  > distortion would be horrible).
                  >
                  > The .63 reducer should work; it does with my LX200 with an AO-7.
                  I don't
                  > know about the optec filters, except that I understand that they
                  will not
                  > work with the CFW-8.
                  >
                  > Mark de Regt
                  > Redmond, Washington, USA
                  > 47.7 N. Latitude; 122 West Longitude
                  > Astro Images: http://home.earthlink.net/~akilla/MAD
                  >
                  >
                  >
                  >
                  > > -----Original Message-----
                  > > From: uwpf23 [mailto:uwpf23@y...]
                  > > Sent: Sunday, November 30, 2003 8:29 PM
                  > > To: ccd-newastro@yahoogroups.com
                  > > Subject: [ccd-newastro] Need focal reducer help!
                  > >
                  > >
                  > > Hi,
                  > > I cannot achieve focus with a Meade F/3.3 focal reducer used with
                  > > the following:
                  > > 1) Celestron CGE-1400 OTA. 3910mm focal length @ F-11 when no
                  focal
                  > > reducer used.
                  > > 2) CCD setup is an ST-7/CFW-8/AO-7 all attached together.
                  > > 3) JMI SmartFocus elecric micro-focuser.
                  > >
                  > > I've tried the following already:
                  > > 1) Mounted the reducer directly onto the visual back of the OTA
                  first,
                  > > then attached the JMI, then the CCD gear. Racked the Celestron
                  > > main focus knob all the way clockwise (mirror moved all the
                  way
                  > > back toward the rear). The image was moving toward focus, but
                  > > could not get all the way focused.
                  > > 2) Mounted JMI focuser first, then the reducer, then the CCD
                  gear.
                  > > Same result.
                  > >
                  > > Note: I CAN get focus with the F/3.3 reducer through the
                  eyepiece and
                  > > a star diagonal visually (NO CCD attached).
                  > >
                  > > Is my problem that the focal reducer lens is too far away from
                  the
                  > > CCD chip with all the gear attached? Or, is it too close to the
                  CCD
                  > > chip? It seems from the visual eyepiece check that the reducer
                  is
                  > > too far away from the CCD chip. I can't get it any closer
                  without
                  > > removing some of the CCD attachments, which is not feasible for
                  me
                  > > (can't do without the color wheel or adaptive optics).
                  > >
                  > > Anybody have any ideas on what the cure for this is? If this
                  specific
                  > > focal reducer is incompatible, anybody have any suggestions for
                  brands
                  > > that will work and are faster than F/6.3 (already have a .63 from
                  > > Celestron that works fine--just need shorter focal lengths than
                  this
                  > > with such a long main focal length to work with!). Would like
                  to get
                  > > down to at least F/4 or 4.5 if possible, as F/6.3 just is not
                  > > desirable with some objects on the CGE-1400.
                  > >
                  > > Thanks for any help you all can give me on this!
                  > >
                  > > Clear skies,
                  > > Wade Van Arsdale
                  > > Little Rock, AR.
                  > > (Registered NewAstro Customer)
                  > >
                  > >
                  > >
                  > >
                  > > 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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