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Re: [William Optics] Reducer III and 80mm f/6 lomo triplet

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  • Scott Walker
    Soren I only see the spikes in the word document and not in the jpegs so it is likely an artifact of the convertion. I looked at some test plots for some Canon
    Message 1 of 18 , Aug 31, 2007
      Soren
       
      I only see the spikes in the word document and not in the jpegs so it is likely an artifact of the convertion.
       
      I looked at some test plots for some Canon camera lenses. Even they show degrading in the corners with astigmatism based on MTF plots.
       
      I think your corner stars look pretty good, but we all have are own tolerance levels. You might try the TV TRF-2008, but I do not know if it will be better.
       
      Thanks again for the great report.
       
      Scott walker
      ----- Original Message -----
      Sent: Friday, August 31, 2007 1:26 PM
      Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo triplet


      Thanks! So there is nothing to do about the astigmatism? Each time I
      look at my photos it bugs me more... :)

      I do not see any spikes on the image without the FF. Are they easily
      visible? Is it on the brightest star? (Sadr)

      Søren

      --- In William-Optics@ yahoogroups. com, "Scott Walker" <sdwalker@.. .>
      wrote:
      >
      > Soren
      >
      > The main affect of changing the distance is to change the average
      curvature correction. Your results look like the distance is pretty
      good. You could shim a mm between the FF and the T-mount to see if it
      make things better or worse, but I would not expect a big change, and
      I would not expect any change in astigmatism. Right now your stars
      are near round, maybe a little square. This indicates that the
      average curvature is being well corrected. When the average is off,
      you will see the star elongate. Depending on which way the average is
      off the elongation can be either in the direction that is seen in
      the "with FF" images or turned 90 degrees, \ versus /.
      >
      > Do you see what I mean by the spikes on the center image without
      the FF?
      >
      > Good luck
      >
      > Scott Walker
      > ----- Original Message -----
      > From: Søren Madsen
      > To: William-Optics@ yahoogroups. com
      > Sent: Friday, August 31, 2007 1:08 AM
      > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
      triplet
      >
      >
      >
      > That's very interesting :D
      >
      > From your model, does the astigmatism change with the distance
      from
      > flattener to chip? How?
      >
      > I think you are right about CCD Inspector.
      >
      > Best Regards,
      > Søren
      >
      > --- In William-Optics@ yahoogroups. com, "Scott Walker" <sdwalker@>
      > wrote:
      > >
      > > Hi Soren
      > >
      > > From my testing I think we are truly seeing astigmatism. I have
      done
      > additional testing that shows that one can get a \ or a / on
      different
      > sides of focus. This is a sign of astigmatism. Also I have
      modeled the
      > WO FFIII in ATMOS. It is not a perfect model, but it does show the
      > general behavior of the flattener. The model shows that when the
      field
      > flattener is well matched to the scope, the "average" field
      curvature
      > can be brought to zero but there will be astigmatism. The
      tangential
      > plane curves away from the objective. The sagittal plane curves
      > towards the objective.
      > >
      > > I think your corner stars look pretty good. They are a little
      square
      > or a little X shaped, but much tighter and rounder than without
      the
      > FF. I did notice that there are some spikes and X patterns on the
      > center image without the FF, so some of this is not due to the
      FF. I
      > think I read somewhere that micro lenses on the sensor can cause
      some
      > spikes.
      > >
      > > As for CCD inspector, I think it is just calculates the average
      > FWHM for each star so it really does not care about astigmatism.
      It
      > does not know if the blur is due to being inside or outside of
      focus,
      > it just knows how big the blur is due to the out of focus
      condition.
      > If it sees that the star is saturated it ignores the star.
      > >
      > > Scott Walker
      > > ----- Original Message -----
      > > From: Søren Madsen
      > > To: William-Optics@ yahoogroups. com
      > > Sent: Thursday, August 30, 2007 10:04 PM
      > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
      triplet
      > >
      > >
      > > Hi Scott,
      > >
      > > just saw in CCD inspectors manual that it disregards bloated
      stars, so
      > > I guess my take on the max FWHM was wrong.
      > >
      > > Someone suggested that the apparent astigmatism could be caused
      by
      > > pinched optics in the flattener. What do you think of this, and
      can
      > > one loosen something to avoid this?
      > >
      > > I will try to slightly change the spacing to the flattener, to
      see if
      > > this helps. Don't expect anything too soon...
      > >
      > > Best Regards,
      > > Søren
      > >
      > > --- In William-Optics@ yahoogroups. com, "Scott Walker"
      <sdwalker@>
      > > wrote:
      > > >
      > > > Soren
      > > >
      > > > Thanks for the help. I looked at the CCD inspector sight. I
      found a
      > > gallery of field flatness image. For most of them the percent
      > > curvature is close to the % increase from the min to the max.
      For your
      > > plots this does not seem to work. May be some other CCD
      inspectors
      > > users could help us out.
      > > >
      > > > Thanks again for the great posting. Just because I have a few
      > > questions does not mean I don't appreciate your fine work.
      > > >
      > > > Scott Walker
      > > > ----- Original Message -----
      > > > From: Søren Madsen
      > > > To: William-Optics@ yahoogroups. com
      > > > Sent: Tuesday, August 28, 2007 11:45 PM
      > > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
      triplet
      > > >
      > > >
      > > > --- In William-Optics@ yahoogroups. com, "Scott Walker"
      <sdwalker@>
      > > > wrote:
      > > > >
      > > > > Soren
      > > > >
      > > > > Interesting plots but I do not know what they mean. Could
      you
      > > > explain. What does the MIN and MAX represent? What is %
      curvature? I
      > > > know lower is better. I looked at the CCD Inspector web sight
      > but not
      > > > much help there. I do not know how the program treats
      > astigmatism. To
      > > > be complete it should show two surfaces. Is the surface the
      average?
      > > > If it is I would have expected the surface with the FF to be
      nearly
      > > > flat. Any insight would be helpful.
      > > > >
      > > > > Scott
      > > > >
      > > >
      > > > Hi Scott,
      > > >
      > > > sorry, I have no insight. Just played around with the program
      > and Ive
      > > > seen these plots elsewhere, so I thought it would be useful to
      > some or
      > > > just to compare numbers...
      > > >
      > > > The min and max FWHM is, I guess, the FWHM of a fit of a
      Gaussian
      > > > star-profile to the stars in the image. The min value would
      be a
      > > > measure of the resolution in the image and the max likely
      come from
      > > > star bloating of Sadr. I.e. less is better in both values.
      With the
      > > > anti-alias filter and Bayers matrix of the DSLR, I guess the
      min
      > FWHM
      > > > can not come below 2*3.44"=6.88" .
      > > >
      > > > I don't know what the % curvature means. Ive seen some say
      that <10%
      > > > is to be considered essentially "perfect". From the surface
      plots, I
      > > > think you can deduce, that you can lower the "curvature %"
      value
      > a lot
      > > > by cropping a little, say to 2500x2500 pixels.
      > > >
      > > > Regarding astigmatism, I simply don't know...
      > > >
      > > > Best Regards,
      > > > Søren
      > > >
      > >
      >

    • Don Klabunde
      Soren, I just completed a series of tests last night with my SuperApo and WO FF III using a 1mm and 2mm shim. The results are essentially the same as with no
      Message 2 of 18 , Sep 1, 2007
        Soren,

        I just completed a series of tests last night with my SuperApo and WO
        FF III using a 1mm and 2mm shim. The results are essentially the same
        as with no shims (maybe slightly degraded FWHM with a 2mm shim from
        slightly poorer correction of the curvature). As Scott says the
        astigmatism is unaffected.

        I have also just downloaded a test report comparing all three WO FF
        and the TV FF with the SuperAPO (f/6 lomo). The TV FF does not
        exhibit as much astigmatism but does have slightly more
        spherochromatism, which you may find to be less objectionable. It's
        really a matter of taste. Both do a very good job, but neither is
        perfect.

        Don

        --- In William-Optics@yahoogroups.com, Søren Madsen <Soeren@...>
        wrote:
        >
        >
        > Thanks! So there is nothing to do about the astigmatism? Each time
        I
        > look at my photos it bugs me more... :)
        >
        > I do not see any spikes on the image without the FF. Are they
        easily
        > visible? Is it on the brightest star? (Sadr)
        >
        > Søren
        >
        > --- In William-Optics@yahoogroups.com, "Scott Walker" <sdwalker@>
        > wrote:
        > >
        > > Soren
        > >
        > > The main affect of changing the distance is to change the average
        > curvature correction. Your results look like the distance is pretty
        > good. You could shim a mm between the FF and the T-mount to see if
        it
        > make things better or worse, but I would not expect a big change,
        and
        > I would not expect any change in astigmatism. Right now your stars
        > are near round, maybe a little square. This indicates that the
        > average curvature is being well corrected. When the average is off,
        > you will see the star elongate. Depending on which way the average
        is
        > off the elongation can be either in the direction that is seen in
        > the "with FF" images or turned 90 degrees, \ versus /.
        > >
        > > Do you see what I mean by the spikes on the center image without
        > the FF?
        > >
        > > Good luck
        > >
        > > Scott Walker
        > > ----- Original Message -----
        > > From: Søren Madsen
        > > To: William-Optics@yahoogroups.com
        > > Sent: Friday, August 31, 2007 1:08 AM
        > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
        > triplet
        > >
        > >
        > >
        > > That's very interesting :D
        > >
        > > From your model, does the astigmatism change with the distance
        > from
        > > flattener to chip? How?
        > >
        > > I think you are right about CCD Inspector.
        > >
        > > Best Regards,
        > > Søren
        > >
        > > --- In William-Optics@yahoogroups.com, "Scott Walker"
        <sdwalker@>
        > > wrote:
        > > >
        > > > Hi Soren
        > > >
        > > > From my testing I think we are truly seeing astigmatism. I
        have
        > done
        > > additional testing that shows that one can get a \ or a / on
        > different
        > > sides of focus. This is a sign of astigmatism. Also I have
        > modeled the
        > > WO FFIII in ATMOS. It is not a perfect model, but it does show
        the
        > > general behavior of the flattener. The model shows that when
        the
        > field
        > > flattener is well matched to the scope, the "average" field
        > curvature
        > > can be brought to zero but there will be astigmatism. The
        > tangential
        > > plane curves away from the objective. The sagittal plane curves
        > > towards the objective.
        > > >
        > > > I think your corner stars look pretty good. They are a little
        > square
        > > or a little X shaped, but much tighter and rounder than without
        > the
        > > FF. I did notice that there are some spikes and X patterns on
        the
        > > center image without the FF, so some of this is not due to the
        > FF. I
        > > think I read somewhere that micro lenses on the sensor can
        cause
        > some
        > > spikes.
        > > >
        > > > As for CCD inspector, I think it is just calculates the
        average
        > > FWHM for each star so it really does not care about
        astigmatism.
        > It
        > > does not know if the blur is due to being inside or outside of
        > focus,
        > > it just knows how big the blur is due to the out of focus
        > condition.
        > > If it sees that the star is saturated it ignores the star.
        > > >
        > > > Scott Walker
        > > > ----- Original Message -----
        > > > From: Søren Madsen
        > > > To: William-Optics@yahoogroups.com
        > > > Sent: Thursday, August 30, 2007 10:04 PM
        > > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
        > triplet
        > > >
        > > >
        > > > Hi Scott,
        > > >
        > > > just saw in CCD inspectors manual that it disregards bloated
        > stars, so
        > > > I guess my take on the max FWHM was wrong.
        > > >
        > > > Someone suggested that the apparent astigmatism could be
        caused
        > by
        > > > pinched optics in the flattener. What do you think of this,
        and
        > can
        > > > one loosen something to avoid this?
        > > >
        > > > I will try to slightly change the spacing to the flattener,
        to
        > see if
        > > > this helps. Don't expect anything too soon...
        > > >
        > > > Best Regards,
        > > > Søren
        > > >
        > > > --- In William-Optics@yahoogroups.com, "Scott Walker"
        > <sdwalker@>
        > > > wrote:
        > > > >
        > > > > Soren
        > > > >
        > > > > Thanks for the help. I looked at the CCD inspector sight. I
        > found a
        > > > gallery of field flatness image. For most of them the percent
        > > > curvature is close to the % increase from the min to the max.
        > For your
        > > > plots this does not seem to work. May be some other CCD
        > inspectors
        > > > users could help us out.
        > > > >
        > > > > Thanks again for the great posting. Just because I have a
        few
        > > > questions does not mean I don't appreciate your fine work.
        > > > >
        > > > > Scott Walker
        > > > > ----- Original Message -----
        > > > > From: Søren Madsen
        > > > > To: William-Optics@yahoogroups.com
        > > > > Sent: Tuesday, August 28, 2007 11:45 PM
        > > > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
        > triplet
        > > > >
        > > > >
        > > > > --- In William-Optics@yahoogroups.com, "Scott Walker"
        > <sdwalker@>
        > > > > wrote:
        > > > > >
        > > > > > Soren
        > > > > >
        > > > > > Interesting plots but I do not know what they mean. Could
        > you
        > > > > explain. What does the MIN and MAX represent? What is %
        > curvature? I
        > > > > know lower is better. I looked at the CCD Inspector web
        sight
        > > but not
        > > > > much help there. I do not know how the program treats
        > > astigmatism. To
        > > > > be complete it should show two surfaces. Is the surface the
        > average?
        > > > > If it is I would have expected the surface with the FF to
        be
        > nearly
        > > > > flat. Any insight would be helpful.
        > > > > >
        > > > > > Scott
        > > > > >
        > > > >
        > > > > Hi Scott,
        > > > >
        > > > > sorry, I have no insight. Just played around with the
        program
        > > and Ive
        > > > > seen these plots elsewhere, so I thought it would be useful
        to
        > > some or
        > > > > just to compare numbers...
        > > > >
        > > > > The min and max FWHM is, I guess, the FWHM of a fit of a
        > Gaussian
        > > > > star-profile to the stars in the image. The min value would
        > be a
        > > > > measure of the resolution in the image and the max likely
        > come from
        > > > > star bloating of Sadr. I.e. less is better in both values.
        > With the
        > > > > anti-alias filter and Bayers matrix of the DSLR, I guess
        the
        > min
        > > FWHM
        > > > > can not come below 2*3.44"=6.88".
        > > > >
        > > > > I don't know what the % curvature means. Ive seen some say
        > that <10%
        > > > > is to be considered essentially "perfect". From the surface
        > plots, I
        > > > > think you can deduce, that you can lower the "curvature %"
        > value
        > > a lot
        > > > > by cropping a little, say to 2500x2500 pixels.
        > > > >
        > > > > Regarding astigmatism, I simply don't know...
        > > > >
        > > > > Best Regards,
        > > > > Søren
        > > > >
        > > >
        > >
        >
      • Scott Walker
        Don Thanks for the update on the shimming, and for the report on all the FF. Very nice job. Scott Walker ... From: Don Klabunde To:
        Message 3 of 18 , Sep 1, 2007
          Don
           
          Thanks for the update on the shimming, and for the report on all the FF. Very nice job.
           
          Scott Walker
          ----- Original Message -----
          Sent: Saturday, September 01, 2007 10:15 AM
          Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo triplet

          Soren,

          I just completed a series of tests last night with my SuperApo and WO
          FF III using a 1mm and 2mm shim. The results are essentially the same
          as with no shims (maybe slightly degraded FWHM with a 2mm shim from
          slightly poorer correction of the curvature). As Scott says the
          astigmatism is unaffected.

          I have also just downloaded a test report comparing all three WO FF
          and the TV FF with the SuperAPO (f/6 lomo). The TV FF does not
          exhibit as much astigmatism but does have slightly more
          spherochromatism, which you may find to be less objectionable. It's
          really a matter of taste. Both do a very good job, but neither is
          perfect.

          Don

          --- In William-Optics@ yahoogroups. com, Søren Madsen <Soeren@...>
          wrote:
          >
          >
          > Thanks! So there is nothing to do about the astigmatism? Each time
          I
          > look at my photos it bugs me more... :)
          >
          > I do not see any spikes on the image without the FF. Are they
          easily
          > visible? Is it on the brightest star? (Sadr)
          >
          > Søren
          >
          > --- In William-Optics@ yahoogroups. com, "Scott Walker" <sdwalker@>
          > wrote:
          > >
          > > Soren
          > >
          > > The main affect of changing the distance is to change the average
          > curvature correction. Your results look like the distance is pretty
          > good. You could shim a mm between the FF and the T-mount to see if
          it
          > make things better or worse, but I would not expect a big change,
          and
          > I would not expect any change in astigmatism. Right now your stars
          > are near round, maybe a little square. This indicates that the
          > average curvature is being well corrected. When the average is off,
          > you will see the star elongate. Depending on which way the average
          is
          > off the elongation can be either in the direction that is seen in
          > the "with FF" images or turned 90 degrees, \ versus /.
          > >
          > > Do you see what I mean by the spikes on the center image without
          > the FF?
          > >
          > > Good luck
          > >
          > > Scott Walker
          > > ----- Original Message -----
          > > From: Søren Madsen
          > > To: William-Optics@ yahoogroups. com
          > > Sent: Friday, August 31, 2007 1:08 AM
          > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
          > triplet
          > >
          > >
          > >
          > > That's very interesting :D
          > >
          > > From your model, does the astigmatism change with the distance
          > from
          > > flattener to chip? How?
          > >
          > > I think you are right about CCD Inspector.
          > >
          > > Best Regards,
          > > Søren
          > >
          > > --- In William-Optics@ yahoogroups. com, "Scott Walker"
          <sdwalker@>
          > > wrote:
          > > >
          > > > Hi Soren
          > > >
          > > > From my testing I think we are truly seeing astigmatism. I
          have
          > done
          > > additional testing that shows that one can get a \ or a / on
          > different
          > > sides of focus. This is a sign of astigmatism. Also I have
          > modeled the
          > > WO FFIII in ATMOS. It is not a perfect model, but it does show
          the
          > > general behavior of the flattener. The model shows that when
          the
          > field
          > > flattener is well matched to the scope, the "average" field
          > curvature
          > > can be brought to zero but there will be astigmatism. The
          > tangential
          > > plane curves away from the objective. The sagittal plane curves
          > > towards the objective.
          > > >
          > > > I think your corner stars look pretty good. They are a little
          > square
          > > or a little X shaped, but much tighter and rounder than without
          > the
          > > FF. I did notice that there are some spikes and X patterns on
          the
          > > center image without the FF, so some of this is not due to the
          > FF. I
          > > think I read somewhere that micro lenses on the sensor can
          cause
          > some
          > > spikes.
          > > >
          > > > As for CCD inspector, I think it is just calculates the
          average
          > > FWHM for each star so it really does not care about
          astigmatism.
          > It
          > > does not know if the blur is due to being inside or outside of
          > focus,
          > > it just knows how big the blur is due to the out of focus
          > condition.
          > > If it sees that the star is saturated it ignores the star.
          > > >
          > > > Scott Walker
          > > > ----- Original Message -----
          > > > From: Søren Madsen
          > > > To: William-Optics@ yahoogroups. com
          > > > Sent: Thursday, August 30, 2007 10:04 PM
          > > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
          > triplet
          > > >
          > > >
          > > > Hi Scott,
          > > >
          > > > just saw in CCD inspectors manual that it disregards bloated
          > stars, so
          > > > I guess my take on the max FWHM was wrong.
          > > >
          > > > Someone suggested that the apparent astigmatism could be
          caused
          > by
          > > > pinched optics in the flattener. What do you think of this,
          and
          > can
          > > > one loosen something to avoid this?
          > > >
          > > > I will try to slightly change the spacing to the flattener,
          to
          > see if
          > > > this helps. Don't expect anything too soon...
          > > >
          > > > Best Regards,
          > > > Søren
          > > >
          > > > --- In William-Optics@ yahoogroups. com, "Scott Walker"
          > <sdwalker@>
          > > > wrote:
          > > > >
          > > > > Soren
          > > > >
          > > > > Thanks for the help. I looked at the CCD inspector sight. I
          > found a
          > > > gallery of field flatness image. For most of them the percent
          > > > curvature is close to the % increase from the min to the max.
          > For your
          > > > plots this does not seem to work. May be some other CCD
          > inspectors
          > > > users could help us out.
          > > > >
          > > > > Thanks again for the great posting. Just because I have a
          few
          > > > questions does not mean I don't appreciate your fine work.
          > > > >
          > > > > Scott Walker
          > > > > ----- Original Message -----
          > > > > From: Søren Madsen
          > > > > To: William-Optics@ yahoogroups. com
          > > > > Sent: Tuesday, August 28, 2007 11:45 PM
          > > > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
          > triplet
          > > > >
          > > > >
          > > > > --- In William-Optics@ yahoogroups. com, "Scott Walker"
          > <sdwalker@>
          > > > > wrote:
          > > > > >
          > > > > > Soren
          > > > > >
          > > > > > Interesting plots but I do not know what they mean. Could
          > you
          > > > > explain. What does the MIN and MAX represent? What is %
          > curvature? I
          > > > > know lower is better. I looked at the CCD Inspector web
          sight
          > > but not
          > > > > much help there. I do not know how the program treats
          > > astigmatism. To
          > > > > be complete it should show two surfaces. Is the surface the
          > average?
          > > > > If it is I would have expected the surface with the FF to
          be
          > nearly
          > > > > flat. Any insight would be helpful.
          > > > > >
          > > > > > Scott
          > > > > >
          > > > >
          > > > > Hi Scott,
          > > > >
          > > > > sorry, I have no insight. Just played around with the
          program
          > > and Ive
          > > > > seen these plots elsewhere, so I thought it would be useful
          to
          > > some or
          > > > > just to compare numbers...
          > > > >
          > > > > The min and max FWHM is, I guess, the FWHM of a fit of a
          > Gaussian
          > > > > star-profile to the stars in the image. The min value would
          > be a
          > > > > measure of the resolution in the image and the max likely
          > come from
          > > > > star bloating of Sadr. I.e. less is better in both values.
          > With the
          > > > > anti-alias filter and Bayers matrix of the DSLR, I guess
          the
          > min
          > > FWHM
          > > > > can not come below 2*3.44"=6.88" .
          > > > >
          > > > > I don't know what the % curvature means. Ive seen some say
          > that <10%
          > > > > is to be considered essentially "perfect". From the surface
          > plots, I
          > > > > think you can deduce, that you can lower the "curvature %"
          > value
          > > a lot
          > > > > by cropping a little, say to 2500x2500 pixels.
          > > > >
          > > > > Regarding astigmatism, I simply don't know...
          > > > >
          > > > > Best Regards,
          > > > > Søren
          > > > >
          > > >
          > >
          >

        • Scott Walker
          Hi Don I am curious about the degree of astigmatism in the TV FF. One can see a hint of the astigmatism in the FFIII by the slight diamond shape of the corner
          Message 4 of 18 , Sep 1, 2007
            Hi Don
             
            I am curious about the degree of astigmatism in the TV FF. One can see a hint of the astigmatism in the FFIII by the slight diamond shape of the corner stars. The astigmatism is much more noticeable when slightly "inside" or "outside" of focus. Here the corner stars become very oval and the oval rotates 90 degree between the inside and outside condition. Can you tell me if the TV FF behaves this way, or do the corner stars stay round and just change size as a function of focus?
             
            Thanks
             
            Scott Walker
            ----- Original Message -----
            Sent: Saturday, September 01, 2007 10:15 AM
            Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo triplet

            Soren,

            I just completed a series of tests last night with my SuperApo and WO
            FF III using a 1mm and 2mm shim. The results are essentially the same
            as with no shims (maybe slightly degraded FWHM with a 2mm shim from
            slightly poorer correction of the curvature). As Scott says the
            astigmatism is unaffected.

            I have also just downloaded a test report comparing all three WO FF
            and the TV FF with the SuperAPO (f/6 lomo). The TV FF does not
            exhibit as much astigmatism but does have slightly more
            spherochromatism, which you may find to be less objectionable. It's
            really a matter of taste. Both do a very good job, but neither is
            perfect.

            Don

            --- In William-Optics@ yahoogroups. com, Søren Madsen <Soeren@...>
            wrote:
            >
            >
            > Thanks! So there is nothing to do about the astigmatism? Each time
            I
            > look at my photos it bugs me more... :)
            >
            > I do not see any spikes on the image without the FF. Are they
            easily
            > visible? Is it on the brightest star? (Sadr)
            >
            > Søren
            >
            > --- In William-Optics@ yahoogroups. com, "Scott Walker" <sdwalker@>
            > wrote:
            > >
            > > Soren
            > >
            > > The main affect of changing the distance is to change the average
            > curvature correction. Your results look like the distance is pretty
            > good. You could shim a mm between the FF and the T-mount to see if
            it
            > make things better or worse, but I would not expect a big change,
            and
            > I would not expect any change in astigmatism. Right now your stars
            > are near round, maybe a little square. This indicates that the
            > average curvature is being well corrected. When the average is off,
            > you will see the star elongate. Depending on which way the average
            is
            > off the elongation can be either in the direction that is seen in
            > the "with FF" images or turned 90 degrees, \ versus /.
            > >
            > > Do you see what I mean by the spikes on the center image without
            > the FF?
            > >
            > > Good luck
            > >
            > > Scott Walker
            > > ----- Original Message -----
            > > From: Søren Madsen
            > > To: William-Optics@ yahoogroups. com
            > > Sent: Friday, August 31, 2007 1:08 AM
            > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
            > triplet
            > >
            > >
            > >
            > > That's very interesting :D
            > >
            > > From your model, does the astigmatism change with the distance
            > from
            > > flattener to chip? How?
            > >
            > > I think you are right about CCD Inspector.
            > >
            > > Best Regards,
            > > Søren
            > >
            > > --- In William-Optics@ yahoogroups. com, "Scott Walker"
            <sdwalker@>
            > > wrote:
            > > >
            > > > Hi Soren
            > > >
            > > > From my testing I think we are truly seeing astigmatism. I
            have
            > done
            > > additional testing that shows that one can get a \ or a / on
            > different
            > > sides of focus. This is a sign of astigmatism. Also I have
            > modeled the
            > > WO FFIII in ATMOS. It is not a perfect model, but it does show
            the
            > > general behavior of the flattener. The model shows that when
            the
            > field
            > > flattener is well matched to the scope, the "average" field
            > curvature
            > > can be brought to zero but there will be astigmatism. The
            > tangential
            > > plane curves away from the objective. The sagittal plane curves
            > > towards the objective.
            > > >
            > > > I think your corner stars look pretty good. They are a little
            > square
            > > or a little X shaped, but much tighter and rounder than without
            > the
            > > FF. I did notice that there are some spikes and X patterns on
            the
            > > center image without the FF, so some of this is not due to the
            > FF. I
            > > think I read somewhere that micro lenses on the sensor can
            cause
            > some
            > > spikes.
            > > >
            > > > As for CCD inspector, I think it is just calculates the
            average
            > > FWHM for each star so it really does not care about
            astigmatism.
            > It
            > > does not know if the blur is due to being inside or outside of
            > focus,
            > > it just knows how big the blur is due to the out of focus
            > condition.
            > > If it sees that the star is saturated it ignores the star.
            > > >
            > > > Scott Walker
            > > > ----- Original Message -----
            > > > From: Søren Madsen
            > > > To: William-Optics@ yahoogroups. com
            > > > Sent: Thursday, August 30, 2007 10:04 PM
            > > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
            > triplet
            > > >
            > > >
            > > > Hi Scott,
            > > >
            > > > just saw in CCD inspectors manual that it disregards bloated
            > stars, so
            > > > I guess my take on the max FWHM was wrong.
            > > >
            > > > Someone suggested that the apparent astigmatism could be
            caused
            > by
            > > > pinched optics in the flattener. What do you think of this,
            and
            > can
            > > > one loosen something to avoid this?
            > > >
            > > > I will try to slightly change the spacing to the flattener,
            to
            > see if
            > > > this helps. Don't expect anything too soon...
            > > >
            > > > Best Regards,
            > > > Søren
            > > >
            > > > --- In William-Optics@ yahoogroups. com, "Scott Walker"
            > <sdwalker@>
            > > > wrote:
            > > > >
            > > > > Soren
            > > > >
            > > > > Thanks for the help. I looked at the CCD inspector sight. I
            > found a
            > > > gallery of field flatness image. For most of them the percent
            > > > curvature is close to the % increase from the min to the max.
            > For your
            > > > plots this does not seem to work. May be some other CCD
            > inspectors
            > > > users could help us out.
            > > > >
            > > > > Thanks again for the great posting. Just because I have a
            few
            > > > questions does not mean I don't appreciate your fine work.
            > > > >
            > > > > Scott Walker
            > > > > ----- Original Message -----
            > > > > From: Søren Madsen
            > > > > To: William-Optics@ yahoogroups. com
            > > > > Sent: Tuesday, August 28, 2007 11:45 PM
            > > > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
            > triplet
            > > > >
            > > > >
            > > > > --- In William-Optics@ yahoogroups. com, "Scott Walker"
            > <sdwalker@>
            > > > > wrote:
            > > > > >
            > > > > > Soren
            > > > > >
            > > > > > Interesting plots but I do not know what they mean. Could
            > you
            > > > > explain. What does the MIN and MAX represent? What is %
            > curvature? I
            > > > > know lower is better. I looked at the CCD Inspector web
            sight
            > > but not
            > > > > much help there. I do not know how the program treats
            > > astigmatism. To
            > > > > be complete it should show two surfaces. Is the surface the
            > average?
            > > > > If it is I would have expected the surface with the FF to
            be
            > nearly
            > > > > flat. Any insight would be helpful.
            > > > > >
            > > > > > Scott
            > > > > >
            > > > >
            > > > > Hi Scott,
            > > > >
            > > > > sorry, I have no insight. Just played around with the
            program
            > > and Ive
            > > > > seen these plots elsewhere, so I thought it would be useful
            to
            > > some or
            > > > > just to compare numbers...
            > > > >
            > > > > The min and max FWHM is, I guess, the FWHM of a fit of a
            > Gaussian
            > > > > star-profile to the stars in the image. The min value would
            > be a
            > > > > measure of the resolution in the image and the max likely
            > come from
            > > > > star bloating of Sadr. I.e. less is better in both values.
            > With the
            > > > > anti-alias filter and Bayers matrix of the DSLR, I guess
            the
            > min
            > > FWHM
            > > > > can not come below 2*3.44"=6.88" .
            > > > >
            > > > > I don't know what the % curvature means. Ive seen some say
            > that <10%
            > > > > is to be considered essentially "perfect". From the surface
            > plots, I
            > > > > think you can deduce, that you can lower the "curvature %"
            > value
            > > a lot
            > > > > by cropping a little, say to 2500x2500 pixels.
            > > > >
            > > > > Regarding astigmatism, I simply don't know...
            > > > >
            > > > > Best Regards,
            > > > > Søren
            > > > >
            > > >
            > >
            >

          • Don Klabunde
            Hi Scott, I did the inside/outside focus testing with WO FF III last night as I tested the shims. It behaves as you would expect for astigmatism. I ll try it
            Message 5 of 18 , Sep 1, 2007
              Hi Scott,

              I did the inside/outside focus testing with WO FF III last night as I
              tested the shims. It behaves as you would expect for astigmatism.
              I'll try it with the TV FF tonight and see what I get.

              Don

              --- In William-Optics@yahoogroups.com, "Scott Walker" <sdwalker@...>
              wrote:
              >
              > Hi Don
              >
              > I am curious about the degree of astigmatism in the TV FF. One can
              see a hint of the astigmatism in the FFIII by the slight diamond
              shape of the corner stars. The astigmatism is much more noticeable
              when slightly "inside" or "outside" of focus. Here the corner stars
              become very oval and the oval rotates 90 degree between the inside
              and outside condition. Can you tell me if the TV FF behaves this way,
              or do the corner stars stay round and just change size as a function
              of focus?
              >
              > Thanks
              >
              > Scott Walker
              > ----- Original Message -----
              > From: Don Klabunde
              > To: William-Optics@yahoogroups.com
              > Sent: Saturday, September 01, 2007 10:15 AM
              > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
              triplet
              >
              >
              > Soren,
              >
              > I just completed a series of tests last night with my SuperApo
              and WO
              > FF III using a 1mm and 2mm shim. The results are essentially the
              same
              > as with no shims (maybe slightly degraded FWHM with a 2mm shim
              from
              > slightly poorer correction of the curvature). As Scott says the
              > astigmatism is unaffected.
              >
              > I have also just downloaded a test report comparing all three WO
              FF
              > and the TV FF with the SuperAPO (f/6 lomo). The TV FF does not
              > exhibit as much astigmatism but does have slightly more
              > spherochromatism, which you may find to be less objectionable.
              It's
              > really a matter of taste. Both do a very good job, but neither is
              > perfect.
              >
              > Don
              >
              > --- In William-Optics@yahoogroups.com, Søren Madsen <Soeren@>
              > wrote:
              > >
              > >
              > > Thanks! So there is nothing to do about the astigmatism? Each
              time
              > I
              > > look at my photos it bugs me more... :)
              > >
              > > I do not see any spikes on the image without the FF. Are they
              > easily
              > > visible? Is it on the brightest star? (Sadr)
              > >
              > > Søren
              > >
              > > --- In William-Optics@yahoogroups.com, "Scott Walker"
              <sdwalker@>
              > > wrote:
              > > >
              > > > Soren
              > > >
              > > > The main affect of changing the distance is to change the
              average
              > > curvature correction. Your results look like the distance is
              pretty
              > > good. You could shim a mm between the FF and the T-mount to see
              if
              > it
              > > make things better or worse, but I would not expect a big
              change,
              > and
              > > I would not expect any change in astigmatism. Right now your
              stars
              > > are near round, maybe a little square. This indicates that the
              > > average curvature is being well corrected. When the average is
              off,
              > > you will see the star elongate. Depending on which way the
              average
              > is
              > > off the elongation can be either in the direction that is seen
              in
              > > the "with FF" images or turned 90 degrees, \ versus /.
              > > >
              > > > Do you see what I mean by the spikes on the center image
              without
              > > the FF?
              > > >
              > > > Good luck
              > > >
              > > > Scott Walker
              > > > ----- Original Message -----
              > > > From: Søren Madsen
              > > > To: William-Optics@yahoogroups.com
              > > > Sent: Friday, August 31, 2007 1:08 AM
              > > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
              > > triplet
              > > >
              > > >
              > > >
              > > > That's very interesting :D
              > > >
              > > > From your model, does the astigmatism change with the
              distance
              > > from
              > > > flattener to chip? How?
              > > >
              > > > I think you are right about CCD Inspector.
              > > >
              > > > Best Regards,
              > > > Søren
              > > >
              > > > --- In William-Optics@yahoogroups.com, "Scott Walker"
              > <sdwalker@>
              > > > wrote:
              > > > >
              > > > > Hi Soren
              > > > >
              > > > > From my testing I think we are truly seeing astigmatism. I
              > have
              > > done
              > > > additional testing that shows that one can get a \ or a / on
              > > different
              > > > sides of focus. This is a sign of astigmatism. Also I have
              > > modeled the
              > > > WO FFIII in ATMOS. It is not a perfect model, but it does
              show
              > the
              > > > general behavior of the flattener. The model shows that when
              > the
              > > field
              > > > flattener is well matched to the scope, the "average" field
              > > curvature
              > > > can be brought to zero but there will be astigmatism. The
              > > tangential
              > > > plane curves away from the objective. The sagittal plane
              curves
              > > > towards the objective.
              > > > >
              > > > > I think your corner stars look pretty good. They are a
              little
              > > square
              > > > or a little X shaped, but much tighter and rounder than
              without
              > > the
              > > > FF. I did notice that there are some spikes and X patterns on
              > the
              > > > center image without the FF, so some of this is not due to
              the
              > > FF. I
              > > > think I read somewhere that micro lenses on the sensor can
              > cause
              > > some
              > > > spikes.
              > > > >
              > > > > As for CCD inspector, I think it is just calculates the
              > average
              > > > FWHM for each star so it really does not care about
              > astigmatism.
              > > It
              > > > does not know if the blur is due to being inside or outside
              of
              > > focus,
              > > > it just knows how big the blur is due to the out of focus
              > > condition.
              > > > If it sees that the star is saturated it ignores the star.
              > > > >
              > > > > Scott Walker
              > > > > ----- Original Message -----
              > > > > From: Søren Madsen
              > > > > To: William-Optics@yahoogroups.com
              > > > > Sent: Thursday, August 30, 2007 10:04 PM
              > > > > Subject: Re: [William Optics] Reducer III and 80mm f/6 lomo
              > > triplet
              > > > >
              > > > >
              > > > > Hi Scott,
              > > > >
              > > > > just saw in CCD inspectors manual that it disregards
              bloated
              > > stars, so
              > > > > I guess my take on the max FWHM was wrong.
              > > > >
              > > > > Someone suggested that the apparent astigmatism could be
              > caused
              > > by
              > > > > pinched optics in the flattener. What do you think of this,
              > and
              > > can
              > > > > one loosen something to avoid this?
              > > > >
              > > > > I will try to slightly change the spacing to the flattener,
              > to
              > > see if
              > > > > this helps. Don't expect anything too soon...
              > > > >
              > > > > Best Regards,
              > > > > Søren
              > > > >
              > > > > --- In William-Optics@yahoogroups.com, "Scott Walker"
              > > <sdwalker@>
              > > > > wrote:
              > > > > >
              > > > > > Soren
              > > > > >
              > > > > > Thanks for the help. I looked at the CCD inspector sight.
              I
              > > found a
              > > > > gallery of field flatness image. For most of them the
              percent
              > > > > curvature is close to the % increase from the min to the
              max.
              > > For your
              > > > > plots this does not seem to work. May be some other CCD
              > > inspectors
              > > > > users could help us out.
              > > > > >
              > > > > > Thanks again for the great posting. Just because I have a
              > few
              > > > > questions does not mean I don't appreciate your fine work.
              > > > > >
              > > > > > Scott Walker
              > > > > > ----- Original Message -----
              > > > > > From: Søren Madsen
              > > > > > To: William-Optics@yahoogroups.com
              > > > > > Sent: Tuesday, August 28, 2007 11:45 PM
              > > > > > Subject: Re: [William Optics] Reducer III and 80mm f/6
              lomo
              > > triplet
              > > > > >
              > > > > >
              > > > > > --- In William-Optics@yahoogroups.com, "Scott Walker"
              > > <sdwalker@>
              > > > > > wrote:
              > > > > > >
              > > > > > > Soren
              > > > > > >
              > > > > > > Interesting plots but I do not know what they mean.
              Could
              > > you
              > > > > > explain. What does the MIN and MAX represent? What is %
              > > curvature? I
              > > > > > know lower is better. I looked at the CCD Inspector web
              > sight
              > > > but not
              > > > > > much help there. I do not know how the program treats
              > > > astigmatism. To
              > > > > > be complete it should show two surfaces. Is the surface
              the
              > > average?
              > > > > > If it is I would have expected the surface with the FF to
              > be
              > > nearly
              > > > > > flat. Any insight would be helpful.
              > > > > > >
              > > > > > > Scott
              > > > > > >
              > > > > >
              > > > > > Hi Scott,
              > > > > >
              > > > > > sorry, I have no insight. Just played around with the
              > program
              > > > and Ive
              > > > > > seen these plots elsewhere, so I thought it would be
              useful
              > to
              > > > some or
              > > > > > just to compare numbers...
              > > > > >
              > > > > > The min and max FWHM is, I guess, the FWHM of a fit of a
              > > Gaussian
              > > > > > star-profile to the stars in the image. The min value
              would
              > > be a
              > > > > > measure of the resolution in the image and the max likely
              > > come from
              > > > > > star bloating of Sadr. I.e. less is better in both
              values.
              > > With the
              > > > > > anti-alias filter and Bayers matrix of the DSLR, I guess
              > the
              > > min
              > > > FWHM
              > > > > > can not come below 2*3.44"=6.88".
              > > > > >
              > > > > > I don't know what the % curvature means. Ive seen some
              say
              > > that <10%
              > > > > > is to be considered essentially "perfect". From the
              surface
              > > plots, I
              > > > > > think you can deduce, that you can lower the "curvature
              %"
              > > value
              > > > a lot
              > > > > > by cropping a little, say to 2500x2500 pixels.
              > > > > >
              > > > > > Regarding astigmatism, I simply don't know...
              > > > > >
              > > > > > Best Regards,
              > > > > > Søren
              > > > > >
              > > > >
              > > >
              > >
              >
            • scottatwin
              Don Thanks. Scott Walker
              Message 6 of 18 , Sep 1, 2007
                Don

                Thanks.

                Scott Walker


                --- In William-Optics@yahoogroups.com, "Don Klabunde" <dpk_faculae@...>
                wrote:
                >
                > Hi Scott,
                >
                > I did the inside/outside focus testing with WO FF III last night as I
                > tested the shims. It behaves as you would expect for astigmatism.
                > I'll try it with the TV FF tonight and see what I get.
                >
                >
              • Don Klabunde
                Hi Scott, I did the inside/outside focus test with the TV FF on the SuperApo last night and comfirms as I suspected the Astigmatism is less than with the WO FF
                Message 7 of 18 , Sep 2, 2007
                  Hi Scott,

                  I did the inside/outside focus test with the TV FF on the SuperApo
                  last night and comfirms as I suspected the Astigmatism is less than
                  with the WO FF III. When I went inside or outside focus by about
                  0.3mm (1/4 turn of the fine focus) the TV FF corner stars had an
                  aspect ratio of 1.3:1 while the WO FF III exhibited a 2.3:1 aspect
                  ratio, significantly more pronounced.

                  Don

                  --- In William-Optics@yahoogroups.com, "scottatwin" <sdwalker@...>
                  wrote:
                  >
                  > Don
                  >
                  > Thanks.
                  >
                  > Scott Walker
                  >
                  >
                  > --- In William-Optics@yahoogroups.com, "Don Klabunde"
                  <dpk_faculae@>
                  > wrote:
                  > >
                  > > Hi Scott,
                  > >
                  > > I did the inside/outside focus testing with WO FF III last night
                  as I
                  > > tested the shims. It behaves as you would expect for astigmatism.
                  > > I'll try it with the TV FF tonight and see what I get.
                  > >
                  > >
                  >
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