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Old 23-09-2009, 06:33 AM
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multiweb (Marc)
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multiweb is offline
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 18,333
Originally Posted by pmrid View Post
Do you mind explaining how you arrived at the figures mentioned - 53.5 and 56 mm? Is it just trial and error or is there a formula?
Yes Peter, trial and error. I took pictures of Alpha Crux centered on the CCD chip and run the subs through CCD Inspector measuring the spacer with an digital caliper.

Originally Posted by pmrid View Post
Also, with the adjudtment rings, did you buy them as a set from Peter Tan or did he have them made up to your design and specifications? Obviously, the idea strikes me as a good one - using the final threaded adjuster with the little lock ring. If someone isn't making this as a set they probably should.
I originally bought the solid spacer he sells for the QHY8, But I couldn't shorten it. I did some test by moving the spacer away and I was over correcting so I figured I had to shorten the distance and in order to do that I needed a shorter spacer. I wasn't ready to stuff around with different lengths rings so I worked out this spacer and send him the drawing see if he could do it and it worked a treat.

I googled all over the place for one and nobody made any. I was really surprised because to me it's just common sense to have an adjustable spacer for field flateners or coma correctors rather than fixed length rings.
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