Flat-Field Exposures

Updated on June 5, 2021, 7:47 pm

Note that several of the Mosaic CCDs have lower full wells than most other CCD at CTIO (~25000-30000 ADU, see Mosaic II home page), so flats with >20,000 ADU are NOT RECOMMENDED.

The flat field system at the Blanco 4m consists of three complete sets of quartz lamps controlled by independent power supplies in the computer room (next to the 4m control room). One of the 3 sets has color balance filters suitable for use with broad band Mosaic filters. The other two sets are useful for narrow-band filter dome flats.

Broad Band Filter Dome Flat Exposure Times

These should be done with only the lamps labeled "color balance" with the voltages set to maximum (16.6 volts).

Filter Exposure
(sec)
Filter Exposure
(sec)
U not
recommended
Sloan u ?
B 30    
V 15 Sloan g 12
R 10 Sloan r 10
I 8 Sloan i 9
Wash C 80 Sloan z 8
Wash M 10 Tyson Bj ?
DDO51 100 Tyson ?

Narrow Band Filter Dome Flat Exposure Times

These should be done with all the lamps on, with the voltages set to maximum (16.6 volts).sg

Filter Exposure
(sec)
Filter Exposure
(sec)
6563_80 12 3727_50 ?
6650_80 ~12 4990_50 60
9725_80 10