Stacking Photometry Issue

2013-03-07

After some reading through email threads and looking at Eddie's figures, I constructed a similar test/data set. I chose three i-filter stacks along an RA slice at dec = -27, and compared the CAL_PSF_MAG values calculated by the static sky CMF to the median value of CAL_PSF_MAG for those objects in the warp CMFs. This nicely reproduced the figure that Eddie had made. The three positions I chose were (RA,DEC,stack_id) red=(170,-27,1111371), green=(197,-27,1157219), blue=(200,-27,1238704). Based on Eddie's ucal comp figure (reproduced below), the red and green positions sample the area that is mottled with large offsets, and the blue position is a "good" position where the offsets seem small. Constructing the <m_W> - m_SS plot shows that the blue position is good, with a single population scattered around zero:

Based on this figure, I selected the objects with m_SS < 20 AND (<m_W> - m_SS) < -0.25 to isolate the offset magnitudes, and then plotted them on the images:

Red:

Green:

Blue:

Pre 2013-03-07