My Birthday Present

[droege@snapmail.us]

Last night was the first good run where I was able to track a field for a
bunch (39) of exposures.  The I camera was stopped down to 3", the V
camera was wide open.

The plots are for one set of 39 (one was bad or there would have been 40)
100 second exposures.

As you can see, the noise floor is about 0.01 mag for both cameras.  My
plat is to stop down the I camera (so the sky noise is not so high) and
run a longer exposure.  Probably 200 seconds.  This will give about 25
frames in the time I can track.

OK, this just hides the problems due to position in the frame.  I plan to
take data for standard tiles.  There will be overlap regions and the
values will probably not match in the overlap regions.  This is a reason
for always reporting stars by tile.  This is a complication, but what can
you do?  Most will like the way the data looks much better.  It will be
left to the user of the data to figure out how he wants to calibrate this.

I am not fixed on stopping down the I camera.  Different exposures would
do the same thing.  But if I don't do something the I camera will saturate
with long exposure.

Any comments?

Tom Droege

i.png

v.png