Re: [ATM] polish time for 13 inch

["Mitchell R" <funnybone101@embarqmail.com>]

I'm fond of the star test at extremely
high powers along with what I call the 'exaggerated Ronchi' test.

The 'exaggerated Ronchi' test is where you warm the mirror face (warm water
bath) above the room temperature then test immediately.  Even small zonal
problems stand out clearly amidst the churning figure.  After the mirror
cools, these zonal problems are extremely challenging to see.  This test is
a good one for bringing out very small zones and zig-zags or abrupt changes
in the mirror slope's derivative.

Mel Bartels


That's a good tip! I'll have to try it. Just one last question at the
moment. It seems F/3 is one of those "too fast" mirrors for some of us (well
at least for me at the moment.) Have you found that a mirror as fast as the
one your working on can be parabolized to good quality and more importantly
give good views at the eyepiece? I know "good" is a loose term. Is the
amount of coma really as bad as people make it out to be? I have a cheap 2"
eyepiece and there are some little seagulls at the edge but I really don't
mind them at all, especially if I can get a wider FOV. Nothing beats
scanning the entire Milky Way and the wider the FOV the more you can get in
the eyepiece.

Mitch 

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