Photometric Standard Stars

SDSS:

SDSS fields are the best choice for photometric starndard stars since they will cover the whole DECam focal plane. In particular, Stripe 82, which was observed repeatedly by SDSS, is an excellent catalog for calibration containing more than 1 million stars down to magnitudes 19.5, 20.5, 20.5, 20.0, and 18.5 in ugriz, respectively (Ivezic et al. 2007). Stripe 82 is an equatorial stripe covering from RA = 20h34m to RA=4h00m. Thus, portions of Stripe 82 are available during most of the night from June to December. The catalog is available here.


Caveats:
  • This catalog contains photometry in the five SDSS bands ugriz. SDSS has no photometry in the Y band.
  • Since most of the SDSS data was taken in the Northern hemisphere, none of the SDSS fields will be close to the zenith from Cerro Tololo.

The following SDSS fields (courtesy of Douglas Tucker) are observable between January and August and have been matched with UKIDSS to include Y photometry (Y-band data from Vega mags to AB mags via YAB = YVega + 0.634). 

Southern Standard Stars for the u'g'r'i'z' System

Smith, J.A., Allam, S.S, Tucker, D.L, et al. (in preparation) kindly provide access to a pre-publication catalog of standard stars in the southern hemisphere(link is external).

For users with observational programs in the south, these standard fields will be located much closer in the sky to the program fields. However, they are small fields (a few arcminutes wide) that will be covered by just one of the DECam CCDs. Thus, they are useful for first order extinction determination but not for zero point differences among the chips.

Notice that for the non-SDSS fields it is advisable to offset the coordinates given in the table to make the whole field to lie within one the CCDs (and not in the gap between the two central CCDs). A shift of 5 arcmin in declination will place the field entirely on CCD N4.