PROCEDURE: 4s

TITLE: Calibration flats

CATEGORY: Calibration

PURPOSE: provide calibration quality (S/N ~ 100) flats.

FREQUENCY: Once for each SBC filter (F140LP, F122M, F115LP, F125LP, 
F150LP, F165LP, PR110L, PR130L), then repeat for first filter (F140LP)
to test stability.

DETECTOR:  SBC 

PREREQUISITES:  (1) SBC safe-open with PtNe lamp. (2) During this note
the minimum amount of attenuation needed for the broadest filter
(F115LP).  

HARDWARE REQUIREMENTS: External stimulus

SOFTWARE REQUIREMENTS: none

COMMAND MODE: PSTOL

PROCEDURE/EXPOSURES: 
           turn-on PtNe lamp on STUFF
           insert diffuser/mirror array.
           Set minimum attenuation for F115LP
	1.    short dark			1000s
	2.    tweak exposure			 120s  
              adjust STUFF attenuation if nec., repeat if nec.
	3-12. long flat				3600s  record diode level
	      repeat 10 times (or more - maximum 15)

VARIANTS:		a: F165LP
			b: F122M
			c: F150LP
			d: F140LP
			e: F125LP
			f: F115LP
			g: PR130L
			h: PR110L

TOTAL EXPOSURES: 12+

TOTAL TIME: setup + tweak + 12-17*overhead + 10-15hrs + 1120s =  10.88-16.04
	(setup = 10min, tweak = 10min, overhead = 2min)

ANALYSIS:  

(1) Verify whether dark is consistent with previous long darks.

(2) Subtract scaled (and smoothed?) master dark from all frames.

(3) Combine flats, and normalize by mean.

(4) Divide normalized flat into individual flats.  Examine for
non-uniformities.