Hi All, i am having issues with increasing number of hot pixels on a ST8300c which are then causing vertical lines on the image. The pixel intensity is so high that it is impossible to use dark frames to remove, but with some dithering it is possible to remove. The camera is about 4 yrs old and worked flawless for the first 2.5 until the first hot pixel appeared. I accepted that this is fact of life with CCDs that occasionally you get such issues but after the long winter here in Canada when i managed to finally get out the other week the hot pixel was gone? The next imaging session it was back as well as another one ! this is making darks and processing an issue now. What are the possibilities it is not camera related ? and any ideas on what to do would be great. I did contact SBig last year about this but i did not get a response which made sense Steve
All CCD sensors are subject to radiation damage over time. The damage typically causes hot pixels and charge traps, which can result in hot columns. I have a camera with a 14 year old KAF-6303E sensor, which was virtually flawless when it was new; it now has over a dozen hot columns, and some of them are really bad. Obviously the rate of damage depends on the radiation exposure. The source of the radiation can be cosmic - rates of degradation are typically higher at higher altitudes as there is less atmospheric shielding - or local. All building materials contain some amount of radioactivity; some materials have substantial amounts. Gypsum board and concrete are two materials that may have significant radioactivity depending on the source materials used to make them. Typically defects are minimized by operating at low temperatures, so cooling the CCD definitely helps. It may also be possible to "anneal" the sensor by baking it; however, I can't recommend doing that unless you can carefully control the temperature. Otherwise you run the risk of destroying the camera. 50 degrees C would be safe, but it is not clear how effective that would be.
