RE: ATM Mirror

[Adam Perkins <scopeguru@yahoo.com>]

> >  Should you grind and polish back of primary
> mirror or should you 
> > leave it along? If you do grind and polish back of
> mirror - do you 
> > use the mirror tool or what do you use? What
> grit/micron size you use,
> > etc.?
> >  Wilber Bandemer  email cndw30a@prodigy.com
> >  Portland,Texas


The threat of astigmatism is always there if you don't grind the back
of a mirror.  I imagine a slightly concave or convex back makes no
difference, but a cylindrical back may lead to serious problems. 
Polishing the back is not necessary for newtonian mirrors.

It seems much easier to grind a blank flat in the beginning than to fix
an astigmatic optic later on.  Whatever you do, work on a "soft"
surface like newspaper or carpet.

Adam Perkins
Covington, Louisiana
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