Re: ATM polishing a small metal disk

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

I wouldn't try to use the reflection off of the pinhole if you want accurate
tracking as the pinhole probably isn't very flat for this purpose.  The bad
thing is that you can't polish the pinhole material because the steel isn't
that thick.  Better that you take a window and use that to get a reflection
of the sun off of it (you'll get about 4% of the light from the incoming
beam if you are perpindicular and more as you increase the angle till you
get to the brewster angle where all of the light is reflected rather than
pass through) and then focus that reflection for your tracking.
I might also note that any polishing of the disk will probably also enlarge
the pinhole
Bob May
http://nav.to/bobmay
bobmay@nethere.com