Re: [ATM] Beginner

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

Most first time mirror grinders find that the job is more boring than
difficult.  The only difficulty is in evaluating the parabola of the mirror
and recent programs take the difficulty of reducing the measurements out of
the picture.
Most of the people that stop attending my class in San Diego do so from the
final bordom of polishing out the mirror so if you get past that point, you
are almost home.  Figuring is sometimes frustrating as most beginners try
figuring for too long of a time before testing and that can be a problem as
the elusive parbola is on the way to other problems that happen with the
distorted shaping of the mirror.
Plate glass is a fine start for the first mirror as it is cheap to get and
work.  Glass shops usually don't stock much in the way of thick glass but
you can get the stuff at the right shop in thicknesses up to 1" which would
be an excellent thickness for a 10" mirror.  You will probably have to edge
the glass as most places will break the edge rather than trepan it
abrasively to the diameter that you want.  I'll note that the more you ask
them to do, the more expensive it will be due to the labor involved.
Diamond tools (like the 4" set of disks at Harbor Freight for about $10 on
sale) will make short work of cutting disks out of the glass.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net


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