The first two plots are for those scans identified as significantly affected by airglow.
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The lines were derived from fits to all the data below, and describe the maximum and minimum slopes of the variation on ~month time scales. Because of the variation of noise with season, one must be careful about "connecting the dots". The lines were picked to show the slope variation, and the full range of intercepts is not shown for clarity. Thus mentally shift the curves as necessary to fit the slopes.
The low points in the J vs. H plot come from 970724 and 970904, with the bulk of the points coming from 971004 and 971005.
The low points in the K vs. H plot comes from 980113, with the values in the high 700s from prior to 970916.
All Coadds From Unconfused Areas
These plots are for all processed coadds that have magnitude thresholds for unconfused areas, which are 15.50, 14.75 and 14.25 mag for J, H and K, respectively. The plots are separated by date, with two nights plotted separately in the next section. On those nights, the points from successive coadds are connected so that the variation with time can be seen.
See those individual nights when attempting to interpret the plots for 23 September - 10 October 1997.
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These plots are for all processed coadds from 971004n and 971005n that have magnitude thresholds for unconfused areas, which are 15.50, 14.75 and 14.25 mag for J, H and K, respectively. The points from successive coadds are connected so that the variation with time can be seen.
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The explicit variation of the H background with time is shown below:
http://spider.ipac.caltech.edu/staff/tchester/2mass/analysis/galaxies/backgrounds/low_density/sky_colors_vs_date.html
Comments and feedback: Tom Chester
Last update: 12 October 1998.