Ben and Steve have discovered that there are structures in the flat images that are changing with time. These were discovered by taking the ratio of flat images taken at different times during the day. This was in conjunction with Steve's effort to identify hot pixels in the flat ratios. Specifically we take the ratio of a flat image with the one take before it.
First, early in the day, the flat ratios do not show any structures.
Later in the day, the flat ratios show distinctive structures, which look like the structures have been translated in the images, so they do not divide out.
One type are round structures that are visible in both cameras.
These seem to be associated with localized fringes only in camera 0. These may be responsible for the localized fringes that we see in some images.
We also observe linear-like trends across the flat ratios which also are a function of time.
We also see a brightening on one side of the flat images changing with time that may be associated with the systematic signals we see on the west side of Level 2 data products.
1079 shows the same pattern. There are trends in the flat ratios in 1079, but possibly not the same increase to the west.
The round structures and fringes are not seen in raw data images, except there is a similar larger round structure near the center of the image.
The large diagonal fringes are seen in raw data images and are not visible in flats.
Questions to answer:
1) Are the structures in all raw flat images or only later in the day? Are they just dividing out early in the day?
2) Are the structures in raw data images? Ben has looked and cannot clearly see them.
Ben and Steve have discovered that there are structures in the flat images that are changing with time. These were discovered by taking the ratio of flat images taken at different times during the day. This was in conjunction with Steve's effort to identify hot pixels in the flat ratios. Specifically we take the ratio of a flat image with the one take before it.
First, early in the day, the flat ratios do not show any structures.
Later in the day, the flat ratios show distinctive structures, which look like the structures have been translated in the images, so they do not divide out.
One type are round structures that are visible in both cameras.
These seem to be associated with localized fringes only in camera 0. These may be responsible for the localized fringes that we see in some images.
We also observe linear-like trends across the flat ratios which also are a function of time.
We also see a brightening on one side of the flat images changing with time that may be associated with the systematic signals we see on the west side of Level 2 data products.
1079 shows the same pattern. There are trends in the flat ratios in 1079, but possibly not the same increase to the west.
The round structures and fringes are not seen in raw data images, except there is a similar larger round structure near the center of the image.
The large diagonal fringes are seen in raw data images and are not visible in flats.
Questions to answer:
1) Are the structures in all raw flat images or only later in the day? Are they just dividing out early in the day?
2) Are the structures in raw data images? Ben has looked and cannot clearly see them.