Re: [ATM] Video Foucault Testing

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

The zoom lens will do very nicely as you will get to be able to
fill the TV with the image of the mirror which is very nice.  At
5mm you're going to be able to test really fast F2 mirrors if you
want to.
I'll note one thing tho and that is that the micro lenses don't
have a reeally good focus but they do indeed come to a soft
focus.  I don't know whether the problem is that the lenses are
made dirt cheap (Edmund Scientific sells lenses for twenty bucks
apiece!) or that they are just so small that the Airy Disk gets
in the way but I've not seen any of them that were worth any real
amounts of money.
Just looked at the website and I don't believe the price.   The
imager is larger on that thean the little security one board
cameras so be aware that you will need a longer FL lens than what
the micro cameras use which is usually a quarter inch imager.  At
that price, I'd buy the camera adn figure out what lens works
best with it.  Since it comes with a CSS adapter (lens with the
same mouinting as the CS type lens mouints but the back focal
length is different) it makes any  of the cheap lenses readily
available to put on the camera.  I'd not bother trying to buy a
Zoom lens ofr this camera unless you already have a lens at hand
or can find one surplus somewhere.  Dono'[t worry about the auto
iris control as you won't be using that anyway as the iris wants
to be fully open when the camera is behind the knife edge.  I'd
probably go with a two inch lens for a first choice if the imager
is a half inch imager.  Somewhat shorter, maybe thirty five mm is
the imager is a third inch one.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net


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