Oct 2003

Mar 2004 - includes analysis of sky variation

Oct 2003 - Old processing

"New" processing (June 2004) of Oct 2003 photometric grid. (See below for old Jan 2004 processing of this data.)

Observations - The observations (exposures 723825 - 723965, Oct 22-23 2003) are of a star field at 2000+10, 13 exposures in each of u*g'r'i'z'. The 13 exposures consist of a reference image, 6 shifted images East, and 6 shifted images North. The 6 shifts are 100", 200", 400", 800", 1600", and 3200" (the last doesn't have many stars!!).

Data Reduction - The data was Elixir-processed by J-CC in June 2004. Aperture photometry was done on all objects using SExtractor aperture phot (ap diameter = 25 pix) Bright stars (instrumental mags -12 to -16) were matched astrometrically on the different shifted images using my program 'mscmatch' (run from 'runmsc' with various 'runmsc.filt' files. See notes in mscmatch.f on how to establish shifts (two pass system).

Plots - The plots are separated by filter below. There is a separate sequence of plots for the north shifts and the east shifts. The plots show the difference in magnitude for stars that were observed in the reference and shifted exposure. A few things to note:

• As the shifts get large, you start to lose matched objects on one side of the mosaic (for obvious reasons!).
• The north shifts are organized in mosaic rows; the east shifts are organized by mosaic columns - again for obvious reasons.
• The "chip number" is the chip number on the reference image.