Spectroscopic flats

Below are tables that provide estimates for the maximum number of counts for a given exposure time. Please check the count level before acquiring several flats in a row because the lamp intensity may vary with time and dichroic type. . ...

LRIS BLUE:

Grism Dichroics
Mirror 680 560 500 460
time
(s)		 ADUs
@ Max		 time
(s)		 ADUs
@ Max		 time
(s)		 ADUs
@ Max		 time
(s)		 ADUs
@ Max		 time
(s)		 ADUs
@ Max
300/5000 25 46,000 25 53,000 45 54,000 100 52,000 170 52,000
400/3400 90 50,000 80 53,000 120 58,000 180 55,000 220 52,000
600/4000 150 50,000 150 50,000 150 50,000 -- --- -- ---
1200/3400 300 1,000 300 1,000 300 1,000 300 1,000 300 1,000

LRIS RED:

Internal Halogen Lamp
Grating Time (s) Central Wavelength
(angstroms)		 Max counts (ADUs)
150/7500 1 7500 22,000
300/5000 7500
400/8500 4 7500 35,000
600/5000
600/7500 8 7500 40,000
600/10000 6 9000 50,000
831/8200 10 8000 40,000
900/5500 15 7500 42,000
1200/7500 25 8000 41,000

Deuterium flat lamp:

The Deuterium flat lamp provides UV light to flat field the bluest region of the spectrum. It requires about 5 minutes to warm up. The following is a flat field obtained with the 400/3400 grism, 1 arcsecond slit, and 30 seconds of exposure.