Re: [ATM] webcam and foucault test?

["David Bevel" <dhcb@bellsouth.net>]

>   I am thinking of resurrecting my knife edge foucault tester to do some
> mirrors and would like to simplify my life a bit. It was originally
> made like Richard Berry's version, with a small telescope behind the
> knife edge.
> I've heard of folks, instead, using a webcam behind the knife egde and
> viewing the shadow patterns on a PC screen.
>
>  I have a spare pc lying around and I'd love to try this out.
> Do folks have any advice as to what type webcam to use?
> other advice?

Hi Robert,

I have the very same tester and just started using my Minolta-Konica Xg
camera with it.  I haven't tried a web cam.  Biggest problem I had was a 
need to
disassemble the scope and clean the lenses. Horribly dirty! I placed the 
camera
lens on a platform directly behind the scope and adjust till I can see the 
image.
Then enlarge to fill the LCD viewing screen. The cool part is the focus 
adjustment
is done internally instead of with an external lens moving in and out.  I 
often
wondered if the low resolution web cams get enough detail for a good data
analysis. I assume that must be so. The camera only confirmed what my eye 
saw.
A big hole in the middle of my 14 inch mirror.  Looks for all the world like 
a hill,
or flattening of the curve; as some prefer, visually. Mr. Foucault, however, 
says hole.
Worry less, Polish, polish, polish!

Dave

_______________________________________________
ATM mailing list http://www.atmlist.net/