Quantitative information about variations in the background at J and K' are
presented and used to develop guidelines for the acquisition and reduction of
ground-based images of faint extended sources in the near-infrared, especially
those which occupy a significant fraction of the field of view of a detector or
which are located in areas crowded with foreground or background sources.
Findings are based primarily upon data acquired over three photometric nights
with the 3.6x3.6 arcmin CFHT-IR array on the Canada-France-Hawaii Telescope
atop Mauna Kea. Although some results are specific to CFHT, overall conclusions
should be useful in guiding observing and reduction strategies of extended
objects elsewhere.Comment: Accepted for publication in PASP July 2004. 29 pages, including 2
tables and 9 figure
