Re: [ATM] mirror grinding

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

I don't think that your magnifying glass really is 5x otherwise you'd be
seeing almost the same things as the 25mm lens would.  A 1" focal length
lens produces 10X power and you rally can't have that big of a lens at that
power.  I'll note that when you say magnifying glass, most assume a lens in
a holder like what Sherlock Holmes uses.
The mirror surface shouldn't have any scratches on it.  The scratches that
you have are possibly from chipping from a sharp edge on the glass or
letting the abrasives get too dry and full of glass fragments.  With the
finer grits, it is way too easy to run a wet too long and end up with more
glass than grit in the abrasive mix.
For the fine grits, the best way that I've found for finding out if a grit
is done is to glancingly reflect a light off of the surface and see if the
surface is reflecting the light equally from one side to another of the
surface.  You want to use a incadescent light or a reflection of the sun
from something like a car windshield.  Increase the angle of reflection
until the light turns orange and the difference in orangeness determines the
finish of the surface with oranger being coarser.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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