Re: [ATM] Improving my focault tester / testing skills

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

I took a o'scope in one day and looked at the siganl on it from a
camera.  I had a lot of trouble seeing one line so I basically
gave it up.  I could see in general the bumps in intensity from
one part to another but I needed to mask off the whole FOV of the
camera and let in lnly a few lines to really get anywhere.  The
whole thing was so cumbersome that I decided not to pursure it.
The idea of frame grabbing a picture would have worked well but I
couldn't keep the equipment there at the lab that I was working
in so that experiment stopped.  Another problem with the
experiment is that the scope  was seeing a nonrestored image
level so the level on the scope was bouncing all around as the
trace averaged itself out from line to line - basicall an AC
connected signal that varied caused this problem which is pretty
typical of video signals that aren't DC restored to where the
black level is 0V.  A surmountable problem when you have the
ability to keep the hardware in one place but not there at that
lab where I had to remove everything at the end of the session.
Many of the picture programs will allow you to see the pixel
values that are under the curso so you can thus readout what the
values are and compare them against another region of the image
which can be a quick way to prove out what you are interested in.
Bob May

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


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