Target Selection of F Star Photometric Standards

We select F type stars as photometric standards. In the following, we use PSF magnitudes. Magnitudes are extinction corrected linear mags defined as

    m = 22.5 - 2.5*alog10( psf_flux )
    m = m - extinction

Star Selection

We select stars by demanding objc_type == 6.

Flag Cuts

F star standards must be

    STATIONARY     in OBJECT2 objc flags
    SURVEY_PRIMARY in RESOLVE_STATUS flags
    PHOTOMETRIC    in CALIB_STATUS flags.

Standards must not be

    in OBJECT1 objc_flags
        BLENDED, TOO_MANY_PEAKS, CR, SATUR, BADSKY

    in OBJECT2 objc_flags2
        PEAKS_TOO_CLOSE, NOTCHECKED_CENTER SATUR_CENTER, INTERP_CENTER,
        PSF_FLUX_INTERP INTERP

and must fall in these magnitude and color ranges:

15.0 < r < 19
[((u-g) - 0.82)² + ((g-r) - 0.30)² + ((r-i) - 0.09)² + ((i-z) - 0.02)²]^1/2 < 0.08