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RE: [William Optics] Re: WO reducer mark 3 and Megrez 90; problem with miss-shaped stars.

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  • john robert adamson
    Hi I have the same issue with my Megrez 90, still persisting with the WO M3 until funds allow the upgrade. I am not so troubled as I am using a ST8300 which is
    Message 1 of 7 , Aug 27, 2012
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      Hi
      I have the same issue with my Megrez 90, still persisting with the WO M3
      until funds allow the upgrade. I am not so troubled as I am using a ST8300
      which is not a full sized chip

      robert

      -----Original Message-----
      From: William-Optics@yahoogroups.com [mailto:William-Optics@yahoogroups.com]
      On Behalf Of Mikael
      Sent: 26 August 2012 14:08
      To: William-Optics@yahoogroups.com
      Subject: [William Optics] Re: WO reducer mark 3 and Megrez 90; problem with
      miss-shaped stars.

      Hi and thanks for the answer! Astrophotography has been off-season here in
      Sweden until now. I totally forgot about this post until a couple of days
      ago when I had my astrophoto season premiere.

      Clear skies!
      Mikael


      --- In William-Optics@yahoogroups.com, "inZet" <gsordiglioni@...> wrote:
      >
      > The correct distance is 56mm. This is easy on Nikon cameras 46mm
      lens-to-chip distance, plus 10mm T-ring. On Canon, distance is 45mm so you
      have to add a 1mm ring. If the correct distance is not set, you get diamond
      stars at the edges of your image: but you get elonged stars in any case.
      > With large sensors like those of modern DSLRs, field curvature at the
      edges is a serious issue.
      > The WO Type III corrects 80% of the field; the Televue TRF-2005 for 90%;
      the Borg DG-L 0.85 #7887 you get a 100% corrected field.
      > I own your same (amazing!) telescope and I bought the Borg. Never seen
      round stars at the edges on user images taken with our telescope model and
      the WO flatteners. With the Borg, they are perfect.
      >
      > Bye,
      > Gianluca
      >
      >
      > --- In William-Optics@yahoogroups.com, "robert adamson" <j.r.adamson@>
      wrote:
      > >
      > > Hi did anyone provide an answer to this query?
      > >
      > >
      > >
      > > robert
      > >
      > >
      > >
      > > From: William-Optics@yahoogroups.com
      > > [mailto:William-Optics@yahoogroups.com]
      > > On Behalf Of Mikael
      > > Sent: 02 March 2012 15:42
      > > To: William-Optics@yahoogroups.com
      > > Subject: [William Optics] WO reducer mark 3 and Megrez 90; problem
      > > with miss-shaped stars.
      > >
      > >
      > >
      > >
      > >
      > > Hello. I have a Megrez 90 (621mm f/6.9) and a WO 0.8
      > > reducer/flattener mark 3. I am having problems with miss-shaped
      > > stars in the edge of my photos, see an example here.
      > > <http://www.martenssonphoto.se/photo/m101_12.html>
      > >
      > > I got the suggestion that I should try changing the distance between
      > > the camera and the flattener. What is the appropriate distance
      > > between the sensor and the flattener for my system?
      > >
      >




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