FreeLists / az-observing / [AZ-Observing] Re: Image Question

["Tom Polakis" <tpolakis@xxxxxxx>]

> Then the supposedly "better mirrors" of the 25-year-old Coulter optics.

Supposedly is right.  I can't imagine a better time to be a customer for 
a mirror than now.  I have seen consistently excellent -- I'd almost use 
the word "perfect" -- mirrors from Carl Zambuto, Mike Spooner, Steve 
Kennedy, and others.  I doubt that the technology that was available to 
Coulter, or even Cave, even compares.


> ...a dozen places where scattered light is coming into the focal plane,
> and what to do to fix it.

You can't beat a focuser baffle, which if sized correctly can eliminate 
almost all unwanted rays from entering the eyepiece.  Here's a picture:

http://www.c2optical.com/baffle_50.jpg

Baffling pundits also say that the there should be no light coming from 
the ground up to the secondary.  That is accomplishing by sealing off the 
back end of the tube with nothing more than a central hole for a fan to 
blow into.

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