Fringe pattern on CCD N4¶
A number of Y-band images were obtained under OBSTAC control during the bright time at the end of the SV period. I created fringe correction frames from observations on two separate nights to evaluate if the fringe pattern remains constant from night to night. The two datasets I evaluated are from 20121122 (9 observations of MS1a starting with 154495) and 20121124 (9 observations of RXT 2248.7-4431 starting with 155251).
I started with the data processed through firstcut by DESDM for CCD N4. I created object masks and then combined the frames to create fringe frames for each night. The image below shows these two fringe frames, along with the difference of the two. The difference image shows no residual fringe pattern and implies the fringe pattern is quite stable, at least under photometric conditions. The grayscale stretch is +/- 2x the rms in the difference image.
-- Paul Martini, 2 December 2012