An 80 second image on Prompt 4 (I filter) showed concentric rings and troughs in the background. They appeared to
surround the max brighness portion of the unflattened field. What is this? Prompt1 was the source of the above image.
Postscript: in fact this pattern somewhat resembles Munch’s The Scream, which I find a tad disconcerting.
February 27, 2006
I Filter on Prompt4
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This is fringing. Fringing is an interference effect of red/infrared light in the thinned substrate of CCDs. It can (and will be) removed using a master fringe image, similar to making a master super flat image out of several data images. We have not finalized the procedure for removing this effect, but most of it should go away when you do the flat fielding. This is a common artifact on most CCDs used at the far red side of the spectrum.
Comment by Aaron LaCluyze — March 2, 2006 @ 5:39 pm