Affiliation
American Association of Variable Star Observers (AAVSO)
Tue, 02/15/2011 - 20:07
The Bright Star Monitor ST-8XME looks like it has developed a partially blocked column around column 772 (that is, nearly the center of the 1530-pixel-wide CCD. This became visible on images taken on 2011-02-11; all earlier images are ok. We are studying the problem, but be aware that blocked columns will affect photometry for any aperture that includes the blocked column. This was probably due to a cosmic ray hit damaging a CCD pixel around (772,244). This is more likely to occur at Tom Krajci's 9400ft elevation than at sea level, and is a major problem for space-based missions.
Arne
And now? Is the blocked column gone? All's well that ends well?
After redoing bias/dark/flat, we find that the blocked column is "gone"; that is, it is properly compensated for through calibration. The offending pixel remains bad, but is quite obvious when looking at images, so you can avoid it. It is also pretty far from the center of the CCD, so won't affect many people.
Arne