The below examples show difference master calibration lampflats from
July,01 2004 with corresponding frames from June,29 2004. Click on
each image to get enlarged version.
Filter Ks, Camera S27 | Filter H, Camera S27 | Filter J, Camera S28 |
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Since June 05, 2005 we've started seeing changed lampflats with dimming at the edges of the field of view. Below are examples of the master calibration frames from that day taken in filter H, cameras S27 and S13. They are difference images where the reference (from 2004-11-05) was subtracted. The corresponding lampflats for other filters - J and Ks, looked similar.
Filter H, Camera S27 | Filter H, Camera S13 |
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Since beginning of June 2005 we have seen the same kind of pattern in
the lampflats in all filters. There are consistent trend observed: