Star Flat Instructions¶
Here are instructions for taking star flats.
First, this is a list of fields that have stellar densities in the useful range. One of these is reachable at just about any time of year.
RA(2000)=06:40:00 DEC(2000)=-34:00:00 RA(2000)=07:30:00 DEC(2000)=-50:00:00 RA(2000)=13:27:00 DEC(2000)=-48:45:00 (Omega Cen outskirts - our favourite starflat field) RA(2000)=19:00:00 DEC(2000)=-50:00:00 RA(2000)=20:40:00 DEC(2000)=-35:00:00
There are starflat scripts for each filter in the /usr/remote/user/sispi/decam/ExposureScripts/DES/starflats folder (~sispi/decam/ExposureScripts/DES/starflats). They are named Starflat-<filter>.json
You must command the telescope to the desired starting point before running the first script. Initial pointing is not critical (1 arc min is fine). The script then observes at each position with relative positioning.
Each script will end with the telescope in the original position. Only if you abort a script for some reason will you have to manually point the telescope to the starting position before starting another script..
There are 22 exposures in the star-flat sequence, sequence, so it takes ~25 minutes per filter..
The star flats should be done in clear weather, although seeing as poor as 1.5-2" will give data of at least some value. Better seeing is better! And of course less moonlight is better, especially for u,g,r,and VR filters.
Last Modified: A. Walker, 17 Dec 2018.