Re: [ATM] webcam and foucault test?

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

Arian, first try the lens on the wall of the room or something
like that.  When you get focus (and you should as the lens is the
same format as the 6mm typically used in webcams.  After you get
that focus, you can then use it on the Foucault test as the lens
needs to be focused on the mirror under test.
To others on the thread that want to use a large format lens, you
have to remember that the light exits the KE in a cone the same
angle as the light coming from the mirror - there is no bending
of the light at the KE!  You have to be able to "see" all of that
cone with the lens so the closer you can get the lens to  the KE,
the better off you are.
The lens that I'm using right now mostly is a C-mount zoom lens
and it is barely big enough to get behind the KE what with the
front of the lens being buried in the lens cell so far.  I move
the lens left or right by 1/8" and the aperture edge interferes
with the reading of a mirror.  Supprisingly, changing the zoom
doesn't affect the edge of the aperture which is buried in the
middle of the lens at the iris.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

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