Re: [APML] Coma Corrector for 10" f/4.72 Newton

[Scott B <sbarbee@centurytel.net>]

Hey Walter,

First off, does your scope give you a full frame with no vignetting now? 
A coma corrector isn't going to do that for you, so make sure you aren't 
chasing something that your scope can't deliver. I built a 11 3/8" 
 f/4.5 newt, with a 4" focuser which stepped down to 2.7 and 2". I had 
to put a 4" secondary, and I still had some vignetting, so make sure 
your expectations are reasonable. I still have the paracorr I bought for 
it, which was only used one night, as the tube ended up being just a bit 
too weak and had flexure. I'd sure be willing to work something out with 
you on the paracorr.
This is a link to the test pic I shot to test the scope and paracorr. 
The top image is the one with the paracorr and you can see that it does 
increase the magnification just a bit, so would increase your T stop a 
bit also. These pics are raw scans, and were taken with a 30# 14" tube 
on my G-11 in a 20 mph wind, so you may notice some movement but not too 
bad. You can really see the coma in the bottom photo in the left/left 
bottom of the lower pic. By the way, don't try and search around the 
site, I haven't gotten around to working on it in the last year. :o(

http://www.geocities.com/cloudchaser57/astropics/paracorr_comparison.jpg

hope this helps!

Scott B.



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