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Re: [ATM] webcam and foucault test?
I have experimented with a Canon A70 and a Phillips Vesta Pro. Both
yielded Foucault test results similar (same deltas) to my visual tests.
The web cam has a fixed 20mm lens, both the focus and manual settings
are adjusted using a black and white image placed in front of the mirror
to be tested. When used to determine the smoothness of the surface, both
cameras can exceed with I can observe visually. But my statements should
be weighted with the fact that I have not used the setup for final
testing, only to determine if I can start figuring. Dang dog biscuit....
But its looking better all the time...
Tom Polk
-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf
Of Michael Lindner
Sent: Friday, July 21, 2006 2:40 PM
To: atm@atmlist.net
Subject: Re: [ATM] webcam and foucault test?
On Fri July 21 2006 2:10 pm, Mike Lockwood wrote:
> Summary - I much prefer viewing with a small telescope (say 3x).
My experience is quite to the contrary, although I must tell you the
foucault
tester I've used has a very nice Astrovid camera with a 35mm camera zoom
lens
mounted on it. The nice features about this setup are that the image can
be
zoomed until the mirror fills the screen, and the gamma of the camera
can be
adjusted to bring out very subtle details. While the readings from this
setup
are different from what I get by eye with the same tester, the deltas
between
readings are nearly identical, and star tests verify that the tester is
accurate.
No doubt the difference is the bargain webcam versus the $900 Astrovid +
zoom
lens combo. I'm sure there's a happy medium in between. Mike, thanks for
sharing your experience.
Clear skies.
--
Michael Lindner
http://www.starastronomy.org *** http://home.att.net/~mikel
http://www.atmsite.org *** http://www.atmlist.net
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