14 Aug 2018
Last week, the fl16 Sinistro camera (on the Dome A 1m telescope in South Africa) was equipped with a new Archon CCD controller. In the nights following the release of that instrument, from Aug 9 to Aug 13, bad dark frames were acquired which corrupted image calibration. The darks were bad because they were made with the camera shutter open. A result of the corrupted calibration is images with high negative sky backgrounds. ----- We are currently re-processing data acquired on these nights with a valid dark frame. If you have already retrieved fl16 data from the archive, we recommend that you download it again. We apologize for the inconvenience.
We've been aware for months of the variations in inter-exposure times among the SBIG cameras (on the 0.4m telescopes). On "faster" cameras, the inter-exposure time is less than the expected default (14s), which can result in multi-exposure observations completing before the observing window closes. On "slower" cameras, the inter-exposure time can be greater than the expected default, which can result in multi-exposure observations getting cut-off when the window closes. ----- We recently discovered that the "slower" cameras get bogged down when calculating guiding corrections. (The 0.4m telescopes do not have extra guide cameras; they "self-guide".) When we disabled guiding on the "slower" cameras, the inter-exposure times were consistently close to the default. In light of this discovery, we've decided to disable guiding on the 7 "slower" cameras. Exposures for which guiding is set to "On" in the request will still succeed, but the AGSTATE header variable will be set to IDLE.
More news about our fleet of SBIG cameras:
Looking forward, our engineering team will travel to our site in Chile in September. Their primary mission will be to replace the primary mirrors in two of the 1m telescopes. We will let you know when resources at that site will be unavailable.