Curious Pattern

[Tom Droege <tdroege@veriomail.com>]

I have been testing cameras.  I have come across one with a curious 
sensitivity pattern. Camera N 11.  The background on this camera  looks 
almost like a figure 8.  The lines of the 8 are increased in 
sensitivity.  It is not a very large effect.  It appears to be within the 
10% sensitivity variation allowed by the specification.

It is possible that this is some sort of reflection pattern.  The moon is 
out there and might be shining on something that would make this 
pattern.  I let the system run for several hours and the pattern did not 
change.  This leaves my neighbors lights, always an iffy thing to predict.

This just to hint at what flat fielding might entail.  The un-corrected 
screen looks like a big fat beetle with pinchers up to the left and a funny 
eye to the right.  OK, I have been looking at too many clouds.  One will 
have to flat field, and it will have high order residuals, and all that 
ugly stuff.

Most of the CCDs so far have had pretty understandable problems.  Mostly 
spots of lower sensitivity.  There is also the data of disk 15 which is 
mostly due to glue deposits on the cover glass from my use of super glue to 
tack the cover back on when the masking tape gave out.

Just something to think about.

Tom Droege