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Binning for guiding?

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  • larryl
    Hi, Would setting the binning of the guide camera to 1x1 (as opposed to 2x2)give better guiding? Now I use a Starlight Xpress SXV-H9C (color) for guiding and
    Message 1 of 15 , Aug 9, 2013
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      Hi,

      Would setting the binning of the guide camera to 1x1 (as opposed to 2x2)give better guiding?

      Now I use a Starlight Xpress SXV-H9C (color) for guiding and use 2x2 binning to eliminate the Bayer mask. I am considering a monochrome camera so that I could use 1x1 binning.

      Comments please.

      Larry Leitch
    • Mark Acker
      FWIW, I use an SBIG RGH which is monochrome.  Always binned at 2x2 and always superb guiding. Mark ________________________________ From: larryl
      Message 2 of 15 , Aug 9, 2013
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        FWIW, I use an SBIG RGH which is monochrome.  Always binned at 2x2 and always superb guiding.

        Mark


        ________________________________
        From: larryl <k3fit@...>
        To: ccd-newastro@yahoogroups.com
        Sent: Friday, August 9, 2013 6:43 AM
        Subject: [ccd-newastro] Binning for guiding?



         
        Hi,

        Would setting the binning of the guide camera to 1x1 (as opposed to 2x2)give better guiding?

        Now I use a Starlight Xpress SXV-H9C (color) for guiding and use 2x2 binning to eliminate the Bayer mask. I am considering a monochrome camera so that I could use 1x1 binning.

        Comments please.

        Larry Leitch




        [Non-text portions of this message have been removed]
      • Ron Wodaski
        No, and it might even make it worse by making guiding more sensitive to seeing effects. Generally speaking, the typical guiding software is accurate to
        Message 3 of 15 , Aug 9, 2013
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          No, and it might even make it worse by making guiding more sensitive to seeing effects.

          Generally speaking, the typical guiding software is accurate to somewhere around 1/10th to 1/20th of a pixel. Guiding 2x2 or 3x3 is just fine.

          Now this is relative to your imaging camera; if you use an external guider, with a shorter focal length scope, you need to compare the focal length of the guide scope to the imagine scope. If the guiding scope is 1/10th the focal length, then binning would take you pretty far away from the imaging camera's image scale, and binning would not be advisable.

          But if, say, your imaging scope's focal length is 2000mm, and your guide scope is, say, 500mm, that's a 4:1 ratio and 2x2 binning would be fine; you are at 8:1 which is in the safe range.

          Ron Wodaski



          On Aug 9, 2013, at 4:43 AM, larryl <k3fit@...> wrote:

          > Hi,
          >
          > Would setting the binning of the guide camera to 1x1 (as opposed to 2x2)give better guiding?
          >
          > Now I use a Starlight Xpress SXV-H9C (color) for guiding and use 2x2 binning to eliminate the Bayer mask. I am considering a monochrome camera so that I could use 1x1 binning.
          >
          > Comments please.
          >
          > Larry Leitch
          >
          >



          [Non-text portions of this message have been removed]
        • Stan
          ... I m sure you realize that binning does not actually eliminate the Bayer filters, though it does convolve the filter information making it impossible to
          Message 4 of 15 , Aug 9, 2013
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            --- "larryl" <k3fit@...> wrote:
            > Now I use a Starlight Xpress SXV-H9C (color) for guiding and
            > use 2x2 binning to eliminate the Bayer mask.

            I'm sure you realize that binning does not actually eliminate the Bayer filters, though it does convolve the filter information making it impossible to infer a color image. And binning also decreases the impact of read noise, which is especially pronounced in short guide exps.

            If the guide scope is sharp then a Bayer camera can result in erroneous guiding because the undersampled star gets skewed by the filters (binned or not). Try deliberately de-focusing the guide star.

            In general, Bayer cameras are a poor and inappropriate choice for guiding. But it depends on the particulars.

            > I am considering a monochrome camera

            That would increase sensitivity by about 2-3 fold and allow you to use dimmer guide stars than are feasible with the Bayer camera.

            > ... so that I could use 1x1 binning.

            1x1 binning is probably not useful for guiding unless you use a separate guide scope with a much shorter FL than the imaging scope.

            Perhaps the real issue is that you are unsatisfied with the guiding/tracking and hope to improve it? Are you getting elongated stars uniform over the field? Or other symptoms attributable to guide error? If so, perform a whole systems analysis to identify the cause(s) that can range from inappropriate software parms to OTA/guide flexure to unmanageable mount.

            Stan
          • larryl
            Hi, My guiding scope is a MiniBorg 50 with a FL of 250 mm. The imaging scopes are Tak180 500 mm FL, Tak130 1000 mm FL, and AT8-RC 1625 mm FL. The ratios of
            Message 5 of 15 , Aug 9, 2013
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              Hi,

              My guiding scope is a MiniBorg 50 with a FL of 250 mm. The imaging scopes are Tak180 500 mm FL, Tak130 1000 mm FL, and AT8-RC 1625 mm FL. The ratios of image scope to guide scope are: 2, 4, and 6.5.

              Which is more critical: the ratio of image to guide scope focal length or the ratio of image to guide image scale? What would be the max (rule of thumb) ratio?

              I use CCD-AutoPilot and can not tell which star it picks for guiding.

              Most of the time my stars are round. Sometimes, in the same night, the stars will be egg shaped vertically and other subs will be egg shaped horizontally.

              Is the tracking error provided by Maxim a good indicator of tracking performance? The lower the standard deviation the better? The closer the average is to zero the better?

              Thanks.
              Larry

              Stan, it would be nice if when you double click on a star in CCD-Stack that the flatness/eccentricity would be displayed. ;-)


              --- In ccd-newastro@yahoogroups.com, "Stan" <stan_ccd@...> wrote:
              >
              > --- "larryl" <k3fit@> wrote:
              > > Now I use a Starlight Xpress SXV-H9C (color) for guiding and
              > > use 2x2 binning to eliminate the Bayer mask.
              >
              > I'm sure you realize that binning does not actually eliminate the Bayer filters, though it does convolve the filter information making it impossible to infer a color image. And binning also decreases the impact of read noise, which is especially pronounced in short guide exps.
              >
              > If the guide scope is sharp then a Bayer camera can result in erroneous guiding because the undersampled star gets skewed by the filters (binned or not). Try deliberately de-focusing the guide star.
              >
              > In general, Bayer cameras are a poor and inappropriate choice for guiding. But it depends on the particulars.
              >
              > > I am considering a monochrome camera
              >
              > That would increase sensitivity by about 2-3 fold and allow you to use dimmer guide stars than are feasible with the Bayer camera.
              >
              > > ... so that I could use 1x1 binning.
              >
              > 1x1 binning is probably not useful for guiding unless you use a separate guide scope with a much shorter FL than the imaging scope.
              >
              > Perhaps the real issue is that you are unsatisfied with the guiding/tracking and hope to improve it? Are you getting elongated stars uniform over the field? Or other symptoms attributable to guide error? If so, perform a whole systems analysis to identify the cause(s) that can range from inappropriate software parms to OTA/guide flexure to unmanageable mount.
              >
              > Stan
              >
            • Ron Wodaski
              It s a question of accuracy. The scope focal lengths give you an approximate idea. The image scales are accurate. Yes, Maxim s error reporting is extremely
              Message 6 of 15 , Aug 9, 2013
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                It's a question of accuracy. The scope focal lengths give you an approximate idea. The image scales are accurate.

                Yes, Maxim's error reporting is extremely valuable.

                Sent from my iPad

                On Aug 9, 2013, at 12:38 PM, larryl <k3fit@...> wrote:

                > Hi,
                >
                > My guiding scope is a MiniBorg 50 with a FL of 250 mm. The imaging scopes are Tak180 500 mm FL, Tak130 1000 mm FL, and AT8-RC 1625 mm FL. The ratios of image scope to guide scope are: 2, 4, and 6.5.
                >
                > Which is more critical: the ratio of image to guide scope focal length or the ratio of image to guide image scale? What would be the max (rule of thumb) ratio?
                >
                > I use CCD-AutoPilot and can not tell which star it picks for guiding.
                >
                > Most of the time my stars are round. Sometimes, in the same night, the stars will be egg shaped vertically and other subs will be egg shaped horizontally.
                >
                > Is the tracking error provided by Maxim a good indicator of tracking performance? The lower the standard deviation the better? The closer the average is to zero the better?
                >
                > Thanks.
                > Larry
                >
                > Stan, it would be nice if when you double click on a star in CCD-Stack that the flatness/eccentricity would be displayed. ;-)
                >
                > --- In ccd-newastro@yahoogroups.com, "Stan" <stan_ccd@...> wrote:
                > >
                > > --- "larryl" <k3fit@> wrote:
                > > > Now I use a Starlight Xpress SXV-H9C (color) for guiding and
                > > > use 2x2 binning to eliminate the Bayer mask.
                > >
                > > I'm sure you realize that binning does not actually eliminate the Bayer filters, though it does convolve the filter information making it impossible to infer a color image. And binning also decreases the impact of read noise, which is especially pronounced in short guide exps.
                > >
                > > If the guide scope is sharp then a Bayer camera can result in erroneous guiding because the undersampled star gets skewed by the filters (binned or not). Try deliberately de-focusing the guide star.
                > >
                > > In general, Bayer cameras are a poor and inappropriate choice for guiding. But it depends on the particulars.
                > >
                > > > I am considering a monochrome camera
                > >
                > > That would increase sensitivity by about 2-3 fold and allow you to use dimmer guide stars than are feasible with the Bayer camera.
                > >
                > > > ... so that I could use 1x1 binning.
                > >
                > > 1x1 binning is probably not useful for guiding unless you use a separate guide scope with a much shorter FL than the imaging scope.
                > >
                > > Perhaps the real issue is that you are unsatisfied with the guiding/tracking and hope to improve it? Are you getting elongated stars uniform over the field? Or other symptoms attributable to guide error? If so, perform a whole systems analysis to identify the cause(s) that can range from inappropriate software parms to OTA/guide flexure to unmanageable mount.
                > >
                > > Stan
                > >
                >
                >


                [Non-text portions of this message have been removed]
              • Stan
                ... Good idea! Thanks, Stan
                Message 7 of 15 , Aug 9, 2013
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                  --- "larryl" <k3fit@...> wrote:
                  > it would be nice if when you double click on a star in
                  > CCD-Stack that the flatness/eccentricity would be displayed

                  Good idea!

                  Thanks,
                  Stan
                • JoeMize
                  Larry, FL s are ballpark estimates, a more accurate method is to use arc.sec p/pixel ratios of Imaging vs. Guider cameras. As images are downloaded use Maxim s
                  Message 8 of 15 , Aug 10, 2013
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                    Larry, FL's are ballpark estimates, a more accurate method is to use arc.sec
                    p/pixel ratios of Imaging vs. Guider cameras.

                    As images are downloaded use Maxim's Information panel. Properly calibrate
                    the Panel and choose stars which aren't over saturated. Set the Bull's Eye
                    inner circle properly. See documentation for both.

                    Center the Bull's Eye on an isolated star which isn't over saturated and
                    double click the Bull's Eye. Move the Bull's Eye with your arrow keys until
                    the 'Pixel' and 'Maximum' fields match. Then look at the Information
                    Panel's "Flatness" field for how out of round the star is. I move the
                    decimal two places right for easier understanding, percentage of out of
                    round.

                    Tracking causes most out of round stars especially if chasing Seeing because
                    Min Move is too aggressive or guide star exposures are far too short
                    effectively chasing Seeing too. Sometimes in good Seeing and short
                    exposures, 10-20sec, Optics Collimation can be seen in this field too...joe
                    :)


                    "May You Go Among The Imperishable Stars"
                    Joe Mize www.cav-sfo.com
                    Chiefland Astronomy Village (CAV), Fla
                    StarFields Observatory, (SFO).

                    ----- Original Message -----
                    From: "larryl" <k3fit@...>
                    To: <ccd-newastro@yahoogroups.com>
                    Sent: Friday, August 09, 2013 3:38 PM
                    Subject: [ccd-newastro] Re: Binning for guiding?


                    > Hi,
                    >
                    > My guiding scope is a MiniBorg 50 with a FL of 250 mm. The imaging scopes
                    > are Tak180 500 mm FL, Tak130 1000 mm FL, and AT8-RC 1625 mm FL. The ratios
                    > of image scope to guide scope are: 2, 4, and 6.5.
                    >
                    > Which is more critical: the ratio of image to guide scope focal length or
                    > the ratio of image to guide image scale? What would be the max (rule of
                    > thumb) ratio?
                    >
                    > I use CCD-AutoPilot and can not tell which star it picks for guiding.
                    >
                    > Most of the time my stars are round. Sometimes, in the same night, the
                    > stars will be egg shaped vertically and other subs will be egg shaped
                    > horizontally.
                    >
                    > Is the tracking error provided by Maxim a good indicator of tracking
                    > performance? The lower the standard deviation the better? The closer the
                    > average is to zero the better?
                    >
                    > Thanks.
                    > Larry
                    >
                    > Stan, it would be nice if when you double click on a star in CCD-Stack
                    > that the flatness/eccentricity would be displayed. ;-)
                    >
                    >
                    > --- In ccd-newastro@yahoogroups.com, "Stan" <stan_ccd@...> wrote:
                    >>
                    >> --- "larryl" <k3fit@> wrote:
                    >> > Now I use a Starlight Xpress SXV-H9C (color) for guiding and
                    >> > use 2x2 binning to eliminate the Bayer mask.
                    >>
                    >> I'm sure you realize that binning does not actually eliminate the Bayer
                    >> filters, though it does convolve the filter information making it
                    >> impossible to infer a color image. And binning also decreases the impact
                    >> of read noise, which is especially pronounced in short guide exps.
                    >>
                    >> If the guide scope is sharp then a Bayer camera can result in erroneous
                    >> guiding because the undersampled star gets skewed by the filters (binned
                    >> or not). Try deliberately de-focusing the guide star.
                    >>
                    >> In general, Bayer cameras are a poor and inappropriate choice for
                    >> guiding. But it depends on the particulars.
                    >>
                    >> > I am considering a monochrome camera
                    >>
                    >> That would increase sensitivity by about 2-3 fold and allow you to use
                    >> dimmer guide stars than are feasible with the Bayer camera.
                    >>
                    >> > ... so that I could use 1x1 binning.
                    >>
                    >> 1x1 binning is probably not useful for guiding unless you use a separate
                    >> guide scope with a much shorter FL than the imaging scope.
                    >>
                    >> Perhaps the real issue is that you are unsatisfied with the
                    >> guiding/tracking and hope to improve it? Are you getting elongated stars
                    >> uniform over the field? Or other symptoms attributable to guide error? If
                    >> so, perform a whole systems analysis to identify the cause(s) that can
                    >> range from inappropriate software parms to OTA/guide flexure to
                    >> unmanageable mount.
                    >>
                    >> Stan
                    >>
                    >
                    >
                    >
                    >
                    > ------------------------------------
                    >
                    >
                    >
                    >
                    >
                  • Stan
                    ... An external guide scope is the prime candidate for tracking errors for main scope FL 40 (approx.). If the guide software reports modest errors without
                    Message 9 of 15 , Aug 10, 2013
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                      --- "larryl" <k3fit@...> wrote:
                      > My guiding scope is a MiniBorg 50...

                      An external guide scope is the prime candidate for tracking errors for main scope FL > 40" (approx.). If the guide software reports modest errors without much asymmetry but the imaged stars are oblong then guide scope/OTA flexure is the most likely defect.

                      But if the guide software reports large asymmetrical errors (e.g. mostly in R.A.) then the problem is likely with the mount and/or guide parms.

                      There is only a small likelihood that the guide camera is the problem. Except that the use of Bayer could cause spurious errors if the guide star is undersampled (Bayer sampling should be finer than normal sampling due to the effects of the matrix). Try defocusing the guide star (of course you may need to find a brighter star to make up for the spread-out flux).

                      Stan
                    • larryl
                      Joe, Thanks for the info. What would be the desired ratio of image asp to guider asp? Min, max etc? My guider is 10.6 asp (binned 2x2) and the imager runs from
                      Message 10 of 15 , Aug 12, 2013
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                        Joe,

                        Thanks for the info. What would be the desired ratio of image asp to guider asp? Min, max etc? My guider is 10.6 asp (binned 2x2) and the imager runs from 0.69 to 3.22 (3 scopes, 3 cameras).

                        Clear skies!
                        Larry


                        --- In ccd-newastro@yahoogroups.com, "JoeMize" <jmize@...> wrote:
                        >
                        > Larry, FL's are ballpark estimates, a more accurate method is to use arc.sec
                        > p/pixel ratios of Imaging vs. Guider cameras.
                        >
                        > As images are downloaded use Maxim's Information panel. Properly calibrate
                        > the Panel and choose stars which aren't over saturated. Set the Bull's Eye
                        > inner circle properly. See documentation for both.
                        >
                        > Center the Bull's Eye on an isolated star which isn't over saturated and
                        > double click the Bull's Eye. Move the Bull's Eye with your arrow keys until
                        > the 'Pixel' and 'Maximum' fields match. Then look at the Information
                        > Panel's "Flatness" field for how out of round the star is. I move the
                        > decimal two places right for easier understanding, percentage of out of
                        > round.
                        >
                        > Tracking causes most out of round stars especially if chasing Seeing because
                        > Min Move is too aggressive or guide star exposures are far too short
                        > effectively chasing Seeing too. Sometimes in good Seeing and short
                        > exposures, 10-20sec, Optics Collimation can be seen in this field too...joe
                        > :)
                        >
                        >
                        > "May You Go Among The Imperishable Stars"
                        > Joe Mize www.cav-sfo.com
                        > Chiefland Astronomy Village (CAV), Fla
                        > StarFields Observatory, (SFO).
                        >
                        > ----- Original Message -----
                        > From: "larryl" <k3fit@...>
                        > To: <ccd-newastro@yahoogroups.com>
                        > Sent: Friday, August 09, 2013 3:38 PM
                        > Subject: [ccd-newastro] Re: Binning for guiding?
                        >
                        >
                        > > Hi,
                        > >
                        > > My guiding scope is a MiniBorg 50 with a FL of 250 mm. The imaging scopes
                        > > are Tak180 500 mm FL, Tak130 1000 mm FL, and AT8-RC 1625 mm FL. The ratios
                        > > of image scope to guide scope are: 2, 4, and 6.5.
                        > >
                        > > Which is more critical: the ratio of image to guide scope focal length or
                        > > the ratio of image to guide image scale? What would be the max (rule of
                        > > thumb) ratio?
                        > >
                        > > I use CCD-AutoPilot and can not tell which star it picks for guiding.
                        > >
                        > > Most of the time my stars are round. Sometimes, in the same night, the
                        > > stars will be egg shaped vertically and other subs will be egg shaped
                        > > horizontally.
                        > >
                        > > Is the tracking error provided by Maxim a good indicator of tracking
                        > > performance? The lower the standard deviation the better? The closer the
                        > > average is to zero the better?
                        > >
                        > > Thanks.
                        > > Larry
                        > >
                        > > Stan, it would be nice if when you double click on a star in CCD-Stack
                        > > that the flatness/eccentricity would be displayed. ;-)
                        > >
                        > >
                        > > --- In ccd-newastro@yahoogroups.com, "Stan" <stan_ccd@> wrote:
                        > >>
                        > >> --- "larryl" <k3fit@> wrote:
                        > >> > Now I use a Starlight Xpress SXV-H9C (color) for guiding and
                        > >> > use 2x2 binning to eliminate the Bayer mask.
                        > >>
                        > >> I'm sure you realize that binning does not actually eliminate the Bayer
                        > >> filters, though it does convolve the filter information making it
                        > >> impossible to infer a color image. And binning also decreases the impact
                        > >> of read noise, which is especially pronounced in short guide exps.
                        > >>
                        > >> If the guide scope is sharp then a Bayer camera can result in erroneous
                        > >> guiding because the undersampled star gets skewed by the filters (binned
                        > >> or not). Try deliberately de-focusing the guide star.
                        > >>
                        > >> In general, Bayer cameras are a poor and inappropriate choice for
                        > >> guiding. But it depends on the particulars.
                        > >>
                        > >> > I am considering a monochrome camera
                        > >>
                        > >> That would increase sensitivity by about 2-3 fold and allow you to use
                        > >> dimmer guide stars than are feasible with the Bayer camera.
                        > >>
                        > >> > ... so that I could use 1x1 binning.
                        > >>
                        > >> 1x1 binning is probably not useful for guiding unless you use a separate
                        > >> guide scope with a much shorter FL than the imaging scope.
                        > >>
                        > >> Perhaps the real issue is that you are unsatisfied with the
                        > >> guiding/tracking and hope to improve it? Are you getting elongated stars
                        > >> uniform over the field? Or other symptoms attributable to guide error? If
                        > >> so, perform a whole systems analysis to identify the cause(s) that can
                        > >> range from inappropriate software parms to OTA/guide flexure to
                        > >> unmanageable mount.
                        > >>
                        > >> Stan
                        > >>
                        > >
                        > >
                        > >
                        > >
                        > > ------------------------------------
                        > >
                        > >
                        > >
                        > >
                        > >
                        >
                      • JoeMize
                        Personally I m from the old film school where having a guider s sensitivity closely match or exceed the imager is most desirable. Sensitivity in that the
                        Message 11 of 15 , Aug 13, 2013
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                          Personally I'm from the old film school where having a guider's sensitivity
                          closely match or exceed the imager is most desirable. Sensitivity in that
                          the guider will see and correct tracking errors 'before' the imaging camera
                          can record them. If the imaging camera is most sensitive, much lower
                          arc.sec p/pixel, it will record tracking deviations before the guider can
                          makes corrections resulting in ovaled stars.

                          With today's software I'd expect ratios others have suggested acceptable.
                          Just remember to use "Camera to Camera arc.sec p/pix" instead of FL's when
                          figuring your ratios. In the end what imager:guider ratio you choose is
                          your choice...joe :)

                          PS: Ah-Hah! I just picked something else you stated earlier: "Sometimes,
                          in the same night, the stars will be egg shaped vertically and other subs
                          will be egg shaped horizontally."

                          That 'seems' to indicate classic optical astigmatism as a telescope nears
                          and passes beyond focus. If focused on one side of perfect focus, showing
                          vertical ovals, then as temperature shifts the telescope's focus, and
                          astigmatism is present, it could reach a focus position where the stars
                          could become horizontal ovals. You should test the telescope which exhibits
                          such a trait and correct it.
                          http://starizona.com/acb/basics/images/startest_astigmatism.jpg
                          http://starizona.com/acb/basics/using_startesting.aspx


                          "May You Go Among The Imperishable Stars"
                          Joe Mize www.cav-sfo.com
                          Chiefland Astronomy Village (CAV), Fla
                          StarFields Observatory, (SFO).

                          ----- Original Message -----
                          From: "larryl" <k3fit@...>
                          To: <ccd-newastro@yahoogroups.com>
                          Sent: Monday, August 12, 2013 5:38 PM
                          Subject: [ccd-newastro] Re: Binning for guiding?


                          > Joe,
                          >
                          > Thanks for the info. What would be the desired ratio of image asp to
                          > guider asp? Min, max etc? My guider is 10.6 asp (binned 2x2) and the
                          > imager runs from 0.69 to 3.22 (3 scopes, 3 cameras).
                          >
                          > Clear skies!
                          > Larry
                          >
                          >
                          > --- In ccd-newastro@yahoogroups.com, "JoeMize" <jmize@...> wrote:
                          >>
                          >> Larry, FL's are ballpark estimates, a more accurate method is to use
                          >> arc.sec
                          >> p/pixel ratios of Imaging vs. Guider cameras.
                          >>
                          >> As images are downloaded use Maxim's Information panel. Properly
                          >> calibrate
                          >> the Panel and choose stars which aren't over saturated. Set the Bull's
                          >> Eye
                          >> inner circle properly. See documentation for both.
                          >>
                          >> Center the Bull's Eye on an isolated star which isn't over saturated and
                          >> double click the Bull's Eye. Move the Bull's Eye with your arrow keys
                          >> until
                          >> the 'Pixel' and 'Maximum' fields match. Then look at the Information
                          >> Panel's "Flatness" field for how out of round the star is. I move the
                          >> decimal two places right for easier understanding, percentage of out of
                          >> round.
                          >>
                          >> Tracking causes most out of round stars especially if chasing Seeing
                          >> because
                          >> Min Move is too aggressive or guide star exposures are far too short
                          >> effectively chasing Seeing too. Sometimes in good Seeing and short
                          >> exposures, 10-20sec, Optics Collimation can be seen in this field
                          >> too...joe
                          >> :)
                          >>
                          >>
                          >> "May You Go Among The Imperishable Stars"
                          >> Joe Mize www.cav-sfo.com
                          >> Chiefland Astronomy Village (CAV), Fla
                          >> StarFields Observatory, (SFO).
                          >>
                          >> ----- Original Message -----
                          >> From: "larryl" <k3fit@...>
                          >> To: <ccd-newastro@yahoogroups.com>
                          >> Sent: Friday, August 09, 2013 3:38 PM
                          >> Subject: [ccd-newastro] Re: Binning for guiding?
                          >>
                          >>
                          >> > Hi,
                          >> >
                          >> > My guiding scope is a MiniBorg 50 with a FL of 250 mm. The imaging
                          >> > scopes
                          >> > are Tak180 500 mm FL, Tak130 1000 mm FL, and AT8-RC 1625 mm FL. The
                          >> > ratios
                          >> > of image scope to guide scope are: 2, 4, and 6.5.
                          >> >
                          >> > Which is more critical: the ratio of image to guide scope focal length
                          >> > or
                          >> > the ratio of image to guide image scale? What would be the max (rule of
                          >> > thumb) ratio?
                          >> >
                          >> > I use CCD-AutoPilot and can not tell which star it picks for guiding.
                          >> >
                          >> > Most of the time my stars are round. Sometimes, in the same night, the
                          >> > stars will be egg shaped vertically and other subs will be egg shaped
                          >> > horizontally.
                          >> >
                          >> > Is the tracking error provided by Maxim a good indicator of tracking
                          >> > performance? The lower the standard deviation the better? The closer
                          >> > the
                          >> > average is to zero the better?
                          >> >
                          >> > Thanks.
                          >> > Larry
                          >> >
                          >> > Stan, it would be nice if when you double click on a star in CCD-Stack
                          >> > that the flatness/eccentricity would be displayed. ;-)
                          >> >
                          >> >
                          >> > --- In ccd-newastro@yahoogroups.com, "Stan" <stan_ccd@> wrote:
                          >> >>
                          >> >> --- "larryl" <k3fit@> wrote:
                          >> >> > Now I use a Starlight Xpress SXV-H9C (color) for guiding and
                          >> >> > use 2x2 binning to eliminate the Bayer mask.
                          >> >>
                          >> >> I'm sure you realize that binning does not actually eliminate the
                          >> >> Bayer
                          >> >> filters, though it does convolve the filter information making it
                          >> >> impossible to infer a color image. And binning also decreases the
                          >> >> impact
                          >> >> of read noise, which is especially pronounced in short guide exps.
                          >> >>
                          >> >> If the guide scope is sharp then a Bayer camera can result in
                          >> >> erroneous
                          >> >> guiding because the undersampled star gets skewed by the filters
                          >> >> (binned
                          >> >> or not). Try deliberately de-focusing the guide star.
                          >> >>
                          >> >> In general, Bayer cameras are a poor and inappropriate choice for
                          >> >> guiding. But it depends on the particulars.
                          >> >>
                          >> >> > I am considering a monochrome camera
                          >> >>
                          >> >> That would increase sensitivity by about 2-3 fold and allow you to use
                          >> >> dimmer guide stars than are feasible with the Bayer camera.
                          >> >>
                          >> >> > ... so that I could use 1x1 binning.
                          >> >>
                          >> >> 1x1 binning is probably not useful for guiding unless you use a
                          >> >> separate
                          >> >> guide scope with a much shorter FL than the imaging scope.
                          >> >>
                          >> >> Perhaps the real issue is that you are unsatisfied with the
                          >> >> guiding/tracking and hope to improve it? Are you getting elongated
                          >> >> stars
                          >> >> uniform over the field? Or other symptoms attributable to guide error?
                          >> >> If
                          >> >> so, perform a whole systems analysis to identify the cause(s) that can
                          >> >> range from inappropriate software parms to OTA/guide flexure to
                          >> >> unmanageable mount.
                          >> >>
                          >> >> Stan
                          >> >>
                          >> >
                          >> >
                          >> >
                          >> >
                          >> > ------------------------------------
                          >> >
                          >> >
                          >> >
                          >> >
                          >> >
                          >>
                          >
                          >
                          >
                          >
                          > ------------------------------------
                          >
                          >
                          >
                          >
                          >
                        • lmbuck2000
                          i find this topic interesting because i recently started guiding with an sbig e-finder (100mm scope ) mounted (directly) on my 1120mm refractor which in
                          Message 12 of 15 , Aug 13, 2013
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                            i find this topic interesting because i recently started guiding with an sbig e-finder (100mm "scope") mounted (directly) on my 1120mm refractor which "in theory" might not work too well. focal length ratio = 11:1, image scale ratio: 15.26:1.66 (over 9:1 guider to imager).

                            i think there may be more to it than simply image scale ratio and it relates to ron's comment that modern guiding software can guide with 1/10 to 1/20 pixel accuracy. that suggests to me my image scale ratio is not just the physical ratio defined by the pixel size and focal lengths, but is greatly improved by the centroid calculation of the guiding software. if my "centroid scale" is just 1/2 my guider image scale, it seems that makes my guider to scope image scale ratio more like 4.5:1 instead of 9:1. and if my centroid calculation is even better the 1/2 (smaller) the ratio goes down even further.

                            the guide results have been excellent (20min subs, perfectly round stars)

                            Lee


                            --- In ccd-newastro@yahoogroups.com, "JoeMize" <jmize@...> wrote:
                            >
                            > Personally I'm from the old film school where having a guider's sensitivity
                            > closely match or exceed the imager is most desirable. Sensitivity in that
                            > the guider will see and correct tracking errors 'before' the imaging camera
                            > can record them. If the imaging camera is most sensitive, much lower
                            > arc.sec p/pixel, it will record tracking deviations before the guider can
                            > makes corrections resulting in ovaled stars.
                            >
                          • Ron Wodaski
                            Good point about the astigmatism. The optics might need collimation. Ron Wodaski ... [Non-text portions of this message have been removed]
                            Message 13 of 15 , Aug 13, 2013
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                              Good point about the astigmatism. The optics might need collimation.

                              Ron Wodaski



                              On Aug 13, 2013, at 8:21 AM, JoeMize <jmize@...> wrote:

                              > Personally I'm from the old film school where having a guider's sensitivity
                              > closely match or exceed the imager is most desirable. Sensitivity in that
                              > the guider will see and correct tracking errors 'before' the imaging camera
                              > can record them. If the imaging camera is most sensitive, much lower
                              > arc.sec p/pixel, it will record tracking deviations before the guider can
                              > makes corrections resulting in ovaled stars.
                              >
                              > With today's software I'd expect ratios others have suggested acceptable.
                              > Just remember to use "Camera to Camera arc.sec p/pix" instead of FL's when
                              > figuring your ratios. In the end what imager:guider ratio you choose is
                              > your choice...joe :)
                              >
                              > PS: Ah-Hah! I just picked something else you stated earlier: "Sometimes,
                              > in the same night, the stars will be egg shaped vertically and other subs
                              > will be egg shaped horizontally."
                              >
                              > That 'seems' to indicate classic optical astigmatism as a telescope nears
                              > and passes beyond focus. If focused on one side of perfect focus, showing
                              > vertical ovals, then as temperature shifts the telescope's focus, and
                              > astigmatism is present, it could reach a focus position where the stars
                              > could become horizontal ovals. You should test the telescope which exhibits
                              > such a trait and correct it.
                              > http://starizona.com/acb/basics/images/startest_astigmatism.jpg
                              > http://starizona.com/acb/basics/using_startesting.aspx
                              >
                              > "May You Go Among The Imperishable Stars"
                              > Joe Mize www.cav-sfo.com
                              > Chiefland Astronomy Village (CAV), Fla
                              > StarFields Observatory, (SFO).
                              >
                              > ----- Original Message -----
                              > From: "larryl" <k3fit@...>
                              > To: <ccd-newastro@yahoogroups.com>
                              > Sent: Monday, August 12, 2013 5:38 PM
                              > Subject: [ccd-newastro] Re: Binning for guiding?
                              >
                              > > Joe,
                              > >
                              > > Thanks for the info. What would be the desired ratio of image asp to
                              > > guider asp? Min, max etc? My guider is 10.6 asp (binned 2x2) and the
                              > > imager runs from 0.69 to 3.22 (3 scopes, 3 cameras).
                              > >
                              > > Clear skies!
                              > > Larry
                              > >
                              > >
                              > > --- In ccd-newastro@yahoogroups.com, "JoeMize" <jmize@...> wrote:
                              > >>
                              > >> Larry, FL's are ballpark estimates, a more accurate method is to use
                              > >> arc.sec
                              > >> p/pixel ratios of Imaging vs. Guider cameras.
                              > >>
                              > >> As images are downloaded use Maxim's Information panel. Properly
                              > >> calibrate
                              > >> the Panel and choose stars which aren't over saturated. Set the Bull's
                              > >> Eye
                              > >> inner circle properly. See documentation for both.
                              > >>
                              > >> Center the Bull's Eye on an isolated star which isn't over saturated and
                              > >> double click the Bull's Eye. Move the Bull's Eye with your arrow keys
                              > >> until
                              > >> the 'Pixel' and 'Maximum' fields match. Then look at the Information
                              > >> Panel's "Flatness" field for how out of round the star is. I move the
                              > >> decimal two places right for easier understanding, percentage of out of
                              > >> round.
                              > >>
                              > >> Tracking causes most out of round stars especially if chasing Seeing
                              > >> because
                              > >> Min Move is too aggressive or guide star exposures are far too short
                              > >> effectively chasing Seeing too. Sometimes in good Seeing and short
                              > >> exposures, 10-20sec, Optics Collimation can be seen in this field
                              > >> too...joe
                              > >> :)
                              > >>
                              > >>
                              > >> "May You Go Among The Imperishable Stars"
                              > >> Joe Mize www.cav-sfo.com
                              > >> Chiefland Astronomy Village (CAV), Fla
                              > >> StarFields Observatory, (SFO).
                              > >>
                              > >> ----- Original Message -----
                              > >> From: "larryl" <k3fit@...>
                              > >> To: <ccd-newastro@yahoogroups.com>
                              > >> Sent: Friday, August 09, 2013 3:38 PM
                              > >> Subject: [ccd-newastro] Re: Binning for guiding?
                              > >>
                              > >>
                              > >> > Hi,
                              > >> >
                              > >> > My guiding scope is a MiniBorg 50 with a FL of 250 mm. The imaging
                              > >> > scopes
                              > >> > are Tak180 500 mm FL, Tak130 1000 mm FL, and AT8-RC 1625 mm FL. The
                              > >> > ratios
                              > >> > of image scope to guide scope are: 2, 4, and 6.5.
                              > >> >
                              > >> > Which is more critical: the ratio of image to guide scope focal length
                              > >> > or
                              > >> > the ratio of image to guide image scale? What would be the max (rule of
                              > >> > thumb) ratio?
                              > >> >
                              > >> > I use CCD-AutoPilot and can not tell which star it picks for guiding.
                              > >> >
                              > >> > Most of the time my stars are round. Sometimes, in the same night, the
                              > >> > stars will be egg shaped vertically and other subs will be egg shaped
                              > >> > horizontally.
                              > >> >
                              > >> > Is the tracking error provided by Maxim a good indicator of tracking
                              > >> > performance? The lower the standard deviation the better? The closer
                              > >> > the
                              > >> > average is to zero the better?
                              > >> >
                              > >> > Thanks.
                              > >> > Larry
                              > >> >
                              > >> > Stan, it would be nice if when you double click on a star in CCD-Stack
                              > >> > that the flatness/eccentricity would be displayed. ;-)
                              > >> >
                              > >> >
                              > >> > --- In ccd-newastro@yahoogroups.com, "Stan" <stan_ccd@> wrote:
                              > >> >>
                              > >> >> --- "larryl" <k3fit@> wrote:
                              > >> >> > Now I use a Starlight Xpress SXV-H9C (color) for guiding and
                              > >> >> > use 2x2 binning to eliminate the Bayer mask.
                              > >> >>
                              > >> >> I'm sure you realize that binning does not actually eliminate the
                              > >> >> Bayer
                              > >> >> filters, though it does convolve the filter information making it
                              > >> >> impossible to infer a color image. And binning also decreases the
                              > >> >> impact
                              > >> >> of read noise, which is especially pronounced in short guide exps.
                              > >> >>
                              > >> >> If the guide scope is sharp then a Bayer camera can result in
                              > >> >> erroneous
                              > >> >> guiding because the undersampled star gets skewed by the filters
                              > >> >> (binned
                              > >> >> or not). Try deliberately de-focusing the guide star.
                              > >> >>
                              > >> >> In general, Bayer cameras are a poor and inappropriate choice for
                              > >> >> guiding. But it depends on the particulars.
                              > >> >>
                              > >> >> > I am considering a monochrome camera
                              > >> >>
                              > >> >> That would increase sensitivity by about 2-3 fold and allow you to use
                              > >> >> dimmer guide stars than are feasible with the Bayer camera.
                              > >> >>
                              > >> >> > ... so that I could use 1x1 binning.
                              > >> >>
                              > >> >> 1x1 binning is probably not useful for guiding unless you use a
                              > >> >> separate
                              > >> >> guide scope with a much shorter FL than the imaging scope.
                              > >> >>
                              > >> >> Perhaps the real issue is that you are unsatisfied with the
                              > >> >> guiding/tracking and hope to improve it? Are you getting elongated
                              > >> >> stars
                              > >> >> uniform over the field? Or other symptoms attributable to guide error?
                              > >> >> If
                              > >> >> so, perform a whole systems analysis to identify the cause(s) that can
                              > >> >> range from inappropriate software parms to OTA/guide flexure to
                              > >> >> unmanageable mount.
                              > >> >>
                              > >> >> Stan
                              > >> >>
                              > >> >
                              > >> >
                              > >> >
                              > >> >
                              > >> > ------------------------------------
                              > >> >
                              > >> >
                              > >> >
                              > >> >
                              > >> >
                              > >>
                              > >
                              > >
                              > >
                              > >
                              > > ------------------------------------
                              > >
                              > >
                              > >
                              > >
                              > >
                              >
                              >



                              [Non-text portions of this message have been removed]
                            • Ron Wodaski
                              Unless you have differential flexure, guiding would be expected to be good at 9:1 image scale ratio. The only time I failed to get good guiding with the
                              Message 14 of 15 , Aug 13, 2013
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                                Unless you have differential flexure, guiding would be expected to be good at 9:1 image scale ratio.

                                The only time I failed to get good guiding with the eFinder was on a C14. That was just too much. :-)

                                Ron Wodaski



                                On Aug 13, 2013, at 9:02 AM, lmbuck2000 <lmbuck2000@...> wrote:

                                > i find this topic interesting because i recently started guiding with an sbig e-finder (100mm "scope") mounted (directly) on my 1120mm refractor which "in theory" might not work too well. focal length ratio = 11:1, image scale ratio: 15.26:1.66 (over 9:1 guider to imager).
                                >
                                > i think there may be more to it than simply image scale ratio and it relates to ron's comment that modern guiding software can guide with 1/10 to 1/20 pixel accuracy. that suggests to me my image scale ratio is not just the physical ratio defined by the pixel size and focal lengths, but is greatly improved by the centroid calculation of the guiding software. if my "centroid scale" is just 1/2 my guider image scale, it seems that makes my guider to scope image scale ratio more like 4.5:1 instead of 9:1. and if my centroid calculation is even better the 1/2 (smaller) the ratio goes down even further.
                                >
                                > the guide results have been excellent (20min subs, perfectly round stars)
                                >
                                > Lee
                                >
                                > --- In ccd-newastro@yahoogroups.com, "JoeMize" <jmize@...> wrote:
                                > >
                                > > Personally I'm from the old film school where having a guider's sensitivity
                                > > closely match or exceed the imager is most desirable. Sensitivity in that
                                > > the guider will see and correct tracking errors 'before' the imaging camera
                                > > can record them. If the imaging camera is most sensitive, much lower
                                > > arc.sec p/pixel, it will record tracking deviations before the guider can
                                > > makes corrections resulting in ovaled stars.
                                > >
                                >
                                >



                                [Non-text portions of this message have been removed]
                              • CurtisC
                                My SBIG camera is retired, but back in the day I had great results using the eFinder and Remote Guide Head with scopes up to 1200mm FL (the longest I tried).
                                Message 15 of 15 , Aug 13, 2013
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                                  My SBIG camera is "retired," but back in the day I had great results using the eFinder and Remote Guide Head with scopes up to 1200mm FL (the longest I tried). The best part was that I always had lots of guide stars.

                                  --- In ccd-newastro@yahoogroups.com, "lmbuck2000" <lmbuck2000@...> wrote:
                                  >
                                  > i find this topic interesting because i recently started guiding with an sbig e-finder (100mm "scope") mounted (directly) on my 1120mm refractor which "in theory" might not work too well. focal length ratio = 11:1, image scale ratio: 15.26:1.66 (over 9:1 guider to imager).
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