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Old 23-09-2009, 06:13 AM
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pmrid (Peter)
Ageing badly.

pmrid is offline
 
Join Date: May 2008
Location: Bribie Is.
Posts: 3,127
Quote:
Originally Posted by multiweb View Post
Ha... that's another one I got stuck on for months. I ended up getting a custom spacer done from http://www.tan14.com/gears.htm. On my 5" newt I need 53.5mm. On the ED80 closer to 56mm. So I have a telescopic adapter that gives me nearl20mm travel on each side. I posted a pic to this reply.

The nose piece is approx 13mm, the sensor plane is approx 6mm from the outside face of the camera so you already have 19mm there minus 55mm that gives you approx 36mm for the spacer on top of the nose piece.

You will find that keeping the nose piece with the MPCC gives you terrible results on bright stars. Light bounces like crazy and you get secondary reflections everywhere.
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?

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.
Peter.
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