Saturation Improvements

[Tom Droege <tdroege@veriomail.com>]

A plea to CCD-World brought some advice on how to fix the problem with 
saturated stars.  As you may recall, a saturated star at the top of the 
frame has a larger signal than one at the bottom.  A first experiment 
showed that it was only saturation that was changing.  Signals below full 
well were the same at the top and the bottom of the frame.  Advice from Jim 
Janesick showed how to adjust the VVH level.  The procedure is to look at 
blooming and adjust VVH for the maximum signal.  I did this last night by 
looking at a saturated star near the bottom of the frame with various VVH 
levels.  4.1  (old value was 6) volts proved to be best.  With this level, 
the saturated star level is close to the same top and bottom, and the full 
well signal is somewhat larger.  Looks like another bug has been beaten to 
a pulp.

After the tests, I ran the camera for the remainder of the evening and took 
400+ images.  400 have been transferred to CD ROM.  The camera is looking 
at roughly 0 degrees declination and taking a dark plus 9 sky images while 
following the sky.  This takes about 20 minutes.  There are 20 such data 
sets in V and I on disk.

I plan to take this data and make a sample disk.  I propose the following:
2 sets V and I of 9 sky images following the sky plus a 
dark                 40 total 8 MByte images
18 V and I sky images -single exposures of different 
fields                    36 total 8 MByte images
2 additional dark 
images 
            4 total 8 MByte images
Total (full 
disk) 
                          80 Images

This gives 20 images to form sky flats and 4 images to form darks.  I have 
looked and 8 are almost enough for sky flats, 4 are plenty for the darks.

This then gives 20 different images in V and I to examine with one time 
exposures.

It gives two sets of 9 images in V and I taken over about 20 minutes to 
search for rapidly changing objects.  These could also be stacked to 
provide greater sensitivity.

What do you all think?  I could sort out a different mix.  I have so far 
two days of pretty good data taken with the 9+1 format.   I should get a 
little more tonight before the clouds move in.  The 9+1 format does not 
cover the full sky, so it would be hard for me to sort out data of the same 
part of the sky on successive nights.  I am accumulating lots of data 
though, so it could be processed to star lists and studied at that level.

Comments please.

Tom Droege