Re: [ATM] Foucault test camera recommendations

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

Pretty much the exposure time of the camera will be about the
same for the same brightness of the image.  I like still cameras
for taking archive photos of stuff but when you have to go do
work, the video camera does a lot better job.
Polaris makes some cheap ($12 or so and up) video cameras.  The
only problem with these cameras is that you need to do some work
providing power to them and a little wallwart power supply will
do nicely for that purpose.  In addition, the cameras aren't
encased but that just means a few minutes doing woodworking.
Their last problem is that the lens really isn't a good FL for
doing Foucault testing so you really need to remove the lens and
provide another lens of a longer focal length to fill the imager
with the results of the test.  The good side of this is that you
can just use a single lens (you're not worried about color
aberrations as the light source is just a single color and you
can easily focus on that color) and change the focal length
easily by buying another cheap lens or even grinding one out of
plate glass if desired.  A planoconvex lens is all that is
needed.
The video camera is so cheap that you can pretty much consider it
dedicated to the application and not have to worry about the
cost.  Too bad that monitors haven't come down in price to where
you can do the same for them.  I haven't seen any $20 monitors
around other than some surplus sale items that need a fair bit of
knowledge and work to get working.
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.

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