Currently, we are just using stars from SDSS Stripe 82, SDSS Stripe 10, the Southern u'g'r'i'z' Standards. For the SDSS equatorial stripes (Stripe 82 and Stripe 10), we make use of UKIDSS LAS Y-band measurements. (Note, we convert the UKIDSS Y-band data from Vega mags to AB mags via Yab = Yvega + 0.634). Here are the standard star fields recommended for the March - August time frame:
These appear to have good data that would cover the full DECam focal plane in ugrizY. For first-order extinction measures, these fields can be supplemented by the Southern u'g'r'i'z' E-field fields, which only cover about one or two DECam CCDs:
There is a set of scripts on the DECam observing computers for helping one
determine the best set of standards to use at a give time and date.
Perhaps the most useful are:
* decamStdFieldsTimeDate.py (output list of standards with airmass X=1.0-2.10 for a given UT date and time)
* decamStdFieldsPickOneByName.py (generate a json file for a given field and given list of filters).
To run on the DECam observing computers at CTIO:
source ~/dtucker/bin/setup_StdStarFieldPicker.csh (or .bash if you are using bash shell)
decamStdFieldsTimeDate.py --help (for detailed help)
decamStdFieldsTimeDate.py --UT=now (for standard stars accessible right now)
decamStdFieldsTimeDate.py --UT='2013/01/07 00:43' (for standard stars accessible at 00:43UT on Jan 7, 2013)
decamStdFieldsPickOneByName.py --help (for detailed help)
decamStdFieldsPickOneByName.py -v --stdFieldName="E6-A" --filterList="g,r,i,z,Y" --outputFile=./DES_sv_e6a_grizY_preswitchover.json
(for a json file containing the exposure script for standard
field E6-A for filters g,r,i,z,Y)