COMPARISON OF ZEROPOINTS IN THE Hx, Jg and Jc FILTERS

All these observations on 19991228.

Median sky frame subtracted from raw frames.  No flatfielding.

3-sigclip averaged, 5 dithers x 3 loops x 7s.

Standard measured with phot, 5"-7" radius sky annulus, 5" diameter aperture.

Adjusted for airmass using median airmass value during the standard star 
        observation (typical range is 0.005-0.044 airmasses) and corrections
        from Persson et al viz: 0.10, 0.04 magnitudes per airmass in J, H 
        respectively.

Filter  Std     Mag     Airmass Corr.   Persson Zeropt

Hx      9106    -10.18  1.062   0.0425  11.842  22.0645
        9104    -11.24  1.814   0.0726  10.750  22.0626
Jc      9106    -10.01  1.038   0.1038  12.153  22.2668
        9104    -11.19  1.715   0.1715  11.045  22.4065
Jg      9106    -9.38   1.028   0.1028  12.153  21.6358
        9106    -9.41   1.031   0.1031  12.153  21.6661
        9104    -10.50  1.463   0.1463  11.045  21.6913