[Comm2011] test plate system using 9 pointings

[Jeffrey Bout]

Hi all,

I've been busy with checking the coadds overlap of the 9 pointings for
testing the plate_kids_decimal plate system.
In this figure

http://www.astro.rug.nl/~bout/nine_pointings.png

you can see the boundingboxes of sourcelists derived from the coadds.
the overlap between the coadds in RA is around 2.35 arcmin and in DEC
around 7.45 arcmin. The figure already shows that there is little
variation in these numbers.
Whether these overlaps are enough depends on the dither strategy. Each
coadd has 5 dithers with 1.7 arcmin variation in RA and 5.7 arcmin
variation in DEC. These number are smaller than the overlaps between
overlaps, so when coadds are combined to some supercoadds, no areas
with less coverage will appear in the coadd-overlaps.
So I conclude that at low declination the overlap between coadds
following the plate_kids_decimal is enough.

PS: Here a detailplot of RA overlap between coadds with sources (+ and
x of 2 coadds).
http://www.astro.rug.nl/~bout/nine_pointings_detail.png

Jeffrey