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Antares 127mm f6.45 Question

Started by csc, 08/16/2009 07:09AM
Posted 08/16/2009 07:09AM Opening Post
I got one of these OTAs a few years ago when they were being discontinued. It is a great scope for wide field viewing. However, when I look at the moon the sunlit peaks and crater rims are yellow and the shadows are a purplish black. A Sirius MV filter does not seem to improve the views. Does anybody know of any type of filter that will improve the CA on this scope to enable decent lunar viewing? Thanks.

Posted 08/16/2009 10:37AM #1
Thats a pretty fast refractor -- 5 inch F6 -- for an achromat.
Maybe try a strong yellow filter (#15) or a green filter (#56).
Red and blue light are going to have a different focus from green light (CA),
and are not going to focus very sharply (chromo-spherical aberration).

Another idea is to make a mask with a hole in it, and stop
it down to 3" or 4" aperture; a 3" F/11 or a 4" F/8 will have a lot
less CA.