In order to test the stability of the BIAS level of the Apogee CCD camera, zero-second bias frames were taken on several dates, at one or two temperatures. In essence, we wish to test whether the BIAS level of the camera electronics remains constant over time, as well as its statistical error, during the testing period.

Procedure:  

Take a series of 100 bias frames: Run a simple statistical analysis to remove frames with clearly very deviant data points (probably due to cosmic rays). Typically, one frame was eliminated per 100-frame bias testing run. Perform a median-combine on the remaining images -- running a median process eliminates effects from cosmic rays hits -- to create a master bias frame. Run simple statistics on the master bias frame in order to investigate the bias level characteristics from one testing period to another.

All statistical tests are performed over a series of boxes, 300-pixels wide, distributed uniformly across the CCD image, using grid coordinates, in the following pattern:

where the statistical boxes are defined by coordinates:  

Region 1:     [500:1100,2900:3500]    Region 2:   [1700:2300,2900:3500]    Region 3:   [2900:3500,2900:3500]

Region 4:     [500:1100,1700:2300]    Region 5:   [1700:2300,1700:2300]    Region 6:   [2900:3500,1700:2300]

Region 7:       [500:1100,500:1100]    Region 8:     [1700:2300,500:1100]   Region 9:     [2900:3500,500:1100]

Results:

20-Nov-2007; Cooling Temperature = -20C

25-Nov-2007; Cooling Temperature = -15C

15-Dec-2007; Cooling Temperature = -20C