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Imaging on both sides of the meridian?

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  • Rex Repich
    What kind of image problems, if any, can occur from stacking images from both sides of the meridian? Once a transit occurs, do most people keep imaging the
    Message 1 of 10 , Sep 26, 2008
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      What kind of image problems, if any, can occur from stacking images from both sides of the
      meridian? Once a transit occurs, do most people keep imaging the same target or try to keep
      all the images on the same side of the meridian?
    • Mike Siniscalchi
      I use a rotator to change the camera to the correct angle when flipping. Then I continue gathering data. The meridian is prime area for imaging so take
      Message 2 of 10 , Sep 26, 2008
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        I use a rotator to change the camera to the correct angle when
        flipping. Then I continue gathering data. The meridian is prime area
        for imaging so take advantage of it.
        If you don't have a rotator you can manually rotate the camera if
        your OTA has that provision -or- adjust the framing to match the last
        frame before the flip so as not to lose too much edge image. Of
        course with the latter option you will need to locate another guide
        star.

        Mike Siniscalchi

        http://www.helixgate.net

        --- In ccd-newastro@yahoogroups.com, "Rex Repich" <repichr@...> wrote:
        >
        > What kind of image problems, if any, can occur from stacking images
        from both sides of the
        > meridian? Once a transit occurs, do most people keep imaging the
        same target or try to keep
        > all the images on the same side of the meridian?
        >
      • Geof Wingham
        Hi - you must have pretty good weather where you live if you can be that fussy- we have to take them where we can get them. When the sky s good go for it,
        Message 3 of 10 , Sep 26, 2008
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          Hi - you must have pretty good weather where you live if you can be that
          fussy- we have to take them where we can get them. When the sky's good
          go for it, software will handle the alignment of the images whatever
          side they are taken on.



          Cheers

          Geof Wingham



          -----Original Message-----
          From: ccd-newastro@yahoogroups.com [mailto:ccd-newastro@yahoogroups.com]
          On Behalf Of Rex Repich
          Sent: Saturday, 27 September 2008 2:39 p.m.
          To: ccd-newastro@yahoogroups.com
          Subject: [ccd-newastro] Imaging on both sides of the meridian?



          What kind of image problems, if any, can occur from stacking images from
          both sides of the
          meridian? Once a transit occurs, do most people keep imaging the same
          target or try to keep
          all the images on the same side of the meridian?





          [Non-text portions of this message have been removed]
        • maxmsm
          It is no problem at all. Max ... from both sides of the ... target or try to keep
          Message 4 of 10 , Sep 26, 2008
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            It is no problem at all.

            Max



            --- In ccd-newastro@yahoogroups.com, "Rex Repich" <repichr@...> wrote:
            >
            > What kind of image problems, if any, can occur from stacking images
            from both sides of the
            > meridian? Once a transit occurs, do most people keep imaging the same
            target or try to keep
            > all the images on the same side of the meridian?
            >
          • Mike Dodd
            ... I image on both sides. The western images are rotated 180° after the meridian flip (assuming a GEM), so they have to be rotated the same 180° during
            Message 5 of 10 , Sep 27, 2008
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              Rex Repich wrote:
              > What kind of image problems, if any, can occur from stacking images from both sides of the
              > meridian? Once a transit occurs, do most people keep imaging the same target or try to keep
              > all the images on the same side of the meridian?

              I image on both sides. The western images are rotated 180° after the
              meridian flip (assuming a GEM), so they have to be rotated the same 180°
              during processing so they can register with the eastern images. I have a
              Pyxis camera rotator that I sometimes use to rotate the camera 180°
              after the flip. If I do this, all the images are correctly oriented for
              registration during processing.

              Beyond the image rotation, I haven't encountered any unusual issues. I
              do spend a few minutes positioning the target on the camera chip after
              the flip so it matches one of the initial eastern images. This way, I
              don't have to crop-out a large portion of the image, which would have a
              poorer SNR.

              Mike
              -----

              Mike Dodd
              Montpelier, VA USA
              http://astronomy.mdodd.com
            • Stu Beaber
              I do it very similiar to Mike...I use CCDSoft and a few minutes after passing the meridian I do a flip. Then rotate the last image on the eastern side 180
              Message 6 of 10 , Sep 27, 2008
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                I do it very similiar to Mike...I use CCDSoft and a few minutes after passing the meridian I do a flip. Then rotate the last image on the eastern side 180 degrees (image>rotate>custom rotate>180 degrees). I can then use the last eastern (now rotated) image to align my new western image with by small mount movements. It doesn't have to be exact, just close enough to the eye. I usually pull up both (last eastern and first western) images at the same time and compare them side by side. During the processing I'll rotate all eastern (or western) images and after registering, crop off any small areas that don't line up.

                Of course, if you're using a fork mount on a wedge...no problem, just keep on imaging as you cross.

                Stu
                www.wd4sel.com


                ----- Original Message -----
                From: Mike Dodd
                To: ccd-newastro@yahoogroups.com
                Sent: Saturday, September 27, 2008 8:42 AM
                Subject: Re: [ccd-newastro] Imaging on both sides of the meridian?


                Rex Repich wrote:
                > What kind of image problems, if any, can occur from stacking images from both sides of the
                > meridian? Once a transit occurs, do most people keep imaging the same target or try to keep
                > all the images on the same side of the meridian?

                I image on both sides. The western images are rotated 180° after the
                meridian flip (assuming a GEM), so they have to be rotated the same 180°
                during processing so they can register with the eastern images. I have a
                Pyxis camera rotator that I sometimes use to rotate the camera 180°
                after the flip. If I do this, all the images are correctly oriented for
                registration during processing.

                Beyond the image rotation, I haven't encountered any unusual issues. I
                do spend a few minutes positioning the target on the camera chip after
                the flip so it matches one of the initial eastern images. This way, I
                don't have to crop-out a large portion of the image, which would have a
                poorer SNR.

                Mike
                -----

                Mike Dodd
                Montpelier, VA USA
                http://astronomy.mdodd.com





                [Non-text portions of this message have been removed]
              • Sander Pool
                I image on both sides of the meridian quite frequently although the custom limits on my EQASCOM controlled EQ6 allow me to track through the meridian as well,
                Message 7 of 10 , Sep 27, 2008
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                  I image on both sides of the meridian quite frequently although the
                  custom limits on my EQASCOM controlled EQ6 allow me to track through the
                  meridian as well, if I want. I'm surprised to read some folks manually
                  rotate their images so that they can be stacked. I saw this in demos at
                  NEIAC of this year as well. DeepSkyStacker will stack images with
                  arbitrary degrees of rotation, automatically. I realize that once you've
                  spent good money on whatever stacker you use now it's hard to decide not
                  to use it but from what I've seen DSS blows 'em all out of the water. I
                  have AIP4WIN and Nebulosity 1 and 2 and never use their stacking
                  functions. Way too much work. PI-C has a registration feature that can
                  be used to stack together with PixelMath but man that makes my head hurt.

                  If you haven't tried DSS yet, you probably should. It comes with
                  DeepSkyStacker Live which will monitor your incoming images, calculate
                  FWHM and other quality metrics and stack. So as you're watching TV you
                  can see the FWHM graph progressing. I don't have an automated focuser so
                  I can decide when it's time to go outside and quickly refocus with my
                  Bahtinov mask. The graph also shows dx and dy so you can see if you have
                  flexure issues before you've ruined an entire evening.

                  I consider DSS one of the great gifts to astro photographers. Gift
                  because it's free. Pretty incredible.

                  Sander
                • Michael Perata
                  While I now have a rotator, I have been having issues with consistency so I don t use the rotator. I always stacked in CCD Stack but would have a devil of a
                  Message 8 of 10 , Sep 27, 2008
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                    While I now have a rotator, I have been having issues with consistency
                    so I don't use the rotator.

                    I always stacked in CCD Stack but would have a devil of a time if the
                    images were flipped, even after rotating the west image to match the
                    east image.

                    I just upgraded to v1.3.7 and I have absolutely no issues with
                    stacking even with a mixed set of images east/west of meridian).
                    v1.3.7 even stacked a mirror flipped image! It is a two click process
                    and the twenty or so times I have used the current version I have not
                    had a missed alignment.

                    Unfortunately, it is not a free upgrade.

                    Michael in San Jose

                    --- In ccd-newastro@yahoogroups.com, "Rex Repich" <repichr@...> wrote:
                    >
                    > What kind of image problems, if any, can occur from stacking images
                    from both sides of the
                    > meridian? Once a transit occurs, do most people keep imaging the
                    same target or try to keep
                    > all the images on the same side of the meridian?
                    >
                  • maxmsm
                    CCD Stack does not have the easiest registration process for flipped images. I have not tried the latest version. I know ccd inspector 2.0 has a nice
                    Message 9 of 10 , Sep 27, 2008
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                      CCD Stack does not have the easiest registration process for flipped
                      images. I have not tried the latest version.

                      I know ccd inspector 2.0 has a nice registration plug in for stack.
                      However, that's a few hundred extra dollars.

                      I use MaxIM's Astrometric registration.

                      Max


                      --- In ccd-newastro@yahoogroups.com, "Michael Perata" <michael@...>
                      wrote:
                      >
                      > While I now have a rotator, I have been having issues with
                      consistency
                      > so I don't use the rotator.
                      >
                      > I always stacked in CCD Stack but would have a devil of a time if
                      the
                      > images were flipped, even after rotating the west image to match the
                      > east image.
                      >
                      > I just upgraded to v1.3.7 and I have absolutely no issues with
                      > stacking even with a mixed set of images east/west of meridian).
                      > v1.3.7 even stacked a mirror flipped image! It is a two click
                      process
                      > and the twenty or so times I have used the current version I have
                      not
                      > had a missed alignment.
                      >
                      > Unfortunately, it is not a free upgrade.
                      >
                      > Michael in San Jose
                      >
                      > --- In ccd-newastro@yahoogroups.com, "Rex Repich" <repichr@> wrote:
                      > >
                      > > What kind of image problems, if any, can occur from stacking
                      images
                      > from both sides of the
                      > > meridian? Once a transit occurs, do most people keep imaging the
                      > same target or try to keep
                      > > all the images on the same side of the meridian?
                      > >
                      >
                    • Rex Repich
                      Thanks to everyone for the information, it confirmed all the items I was concerned about, Rex Repich ... of the ... to keep
                      Message 10 of 10 , Sep 29, 2008
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                        Thanks to everyone for the information, it confirmed all the items I was concerned about,
                        Rex Repich

                        --- In ccd-newastro@yahoogroups.com, Mike Dodd <mike@...> wrote:
                        >
                        > Rex Repich wrote:
                        > > What kind of image problems, if any, can occur from stacking images from both sides
                        of the
                        > > meridian? Once a transit occurs, do most people keep imaging the same target or try
                        to keep
                        > > all the images on the same side of the meridian?
                        >
                        > I image on both sides. The western images are rotated 180° after the
                        > meridian flip (assuming a GEM), so they have to be rotated the same 180°
                        > during processing so they can register with the eastern images. I have a
                        > Pyxis camera rotator that I sometimes use to rotate the camera 180°
                        > after the flip. If I do this, all the images are correctly oriented for
                        > registration during processing.
                        >
                        > Beyond the image rotation, I haven't encountered any unusual issues. I
                        > do spend a few minutes positioning the target on the camera chip after
                        > the flip so it matches one of the initial eastern images. This way, I
                        > don't have to crop-out a large portion of the image, which would have a
                        > poorer SNR.
                        >
                        > Mike
                        > -----
                        >
                        > Mike Dodd
                        > Montpelier, VA USA
                        > http://astronomy.mdodd.com
                        >
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