Re: [ATM] Video Foucault Testing

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

For Foucault testing, the resolution realy doesn't matter much as
a 3220x200 image will be enough to see the shades of gray.
Digital actually is less sensitive in this respect as it
decimates the gray levels into 256 shades from black to white
although that may be a good thing for some as the steps will be
apparent if you really look close enough.
For Ronchi testin, the somewhat larger CCITT format will do fine
although a full frame image is better.  The thing that saves this
is that the lines of the Ronchi image are fuzzy so that your
resolution of the curves of the lines can be seen well.
The C-mount, as well as the Css mount cameras which are nothing
more than a different back focal length from the C-mount lenses,
are usually of a larger format image sensor which may still have
only the same number of pixels as the smaller micro cameras which
means that they will be more sensitive to light than the smaller
cameras and thus have a "better focus" than the micro cameras.
The problem with those microcamera lenses is that they are so
tiny that the Airy Disk is so large that they might as well be
pinhole lenses and they don't give a good focus.  Put a larger
lens on and the cameras will perform a lot better as the Airy
Disk no becomes smaller than the pixel size and thus the lens can
focus a spot of light to one pixel rather than several pixels.
Interesting that you chose to do a bilevel brightness on your LED
instead of doing a seperate LED for the finder.  We are now using
a bright white LED for the finder and am no able to easily see
the spot from the mirror on the white target.  Bright is indeed a
good quality for the finder LED!
Bob May

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


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