A LOOK AT THE SOUTHERN-HEMISPHERE DARK MEDIANS

DARKS has processed several nights from the southern hemisphere, and canonical responsivities and darks are being produced. The hardware appears to be quite superior to that of the northern hemisphere. Two nights were checked, 980321s and 980328s. The former had 274-frame dark sequences, while the latter's were composed of just 48 frames. In both cases, and in all bands, the dark noise is very small, the medians show no drift, and the startup transients seen in the north are absent. The strange "rising" behavior seen in the northern H band in both morning and evening dark sequences is also absent. These dark sequences were taken in the morning.

Plots of the medians herein use an ordinate range of 40 DN, since that was typical of what was needed for the northern data, and it seemed advisable to use a comparable range for getting a first impression of the south. A much smaller range would have sufficed otherwise.

The dark medians for 980321s bands J, H, and K are shown in Fig.1, Fig.2, and Fig.3, respectively. As in previous plots, the black line shows the frame median as a function of frame number, and the quadrant medians are shown as variously colored diamonds. The dark medians for 980328s bands J, H, and K are shown in Fig.4, Fig5, and Fig.6, respectively.

John W. Fowler
jwf@ipac.caltech.edu
posted May 1, 1998