Re: [ATM] making flats

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

If you're making three flats together, you don't even need a
master flat except to assure youelf that they truley are flat.
Several pages have articles on making flats, including mine, and
the process of measuring them is rather easy.  The problem with
flats is that you need to make a flat surfacce and that is one of
a radius of a real long distance, like to the sun!  The problem
here is that a radius of a hundred feet is not flat and the
difference between a hundred feet and the distance to the sun
isn't that much when it comes to angles.  It's kind of like
making a parabolic mirror to exactly a particular dimension, off
by a thousandth of an inch and the mirror is no good.
The erosion of the glass is where the pressure is highest with
the grit between the two pieces of glass.  You can, if you desire
and understand the technique, make the bottom ghlass concave and
the top convex which is directly opposite conventional wisdom!
Bob May

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


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