Re: [ATM] astigmatism as seen via ronchi?

["Bob May" <rmay@nethere.com>]

Don, when I rotate the Ronchi grating on the stand to see other
angles, I don't see a change in the angles from inside to
outside.  In other words, if I go 45 degrees clockwise with the
grating, the lines are at 45 degrees inside and outside of the
focus with the same 45 degree angle.

One thing I didn't mention in my other post is that a Lurie
Houghton lens is a very thin piece of glass and it is easy to get
all kinds of errors in the surface if you don't support it well.
I'm working with a
13" diameter piece of glass that is only .75" thick at the
thickest and that means that it is near 1/20 ratio!  Thin mirror
techniques are definitely needed in dealing with this!Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net


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