A Dark Frame
A Dark Frame: This is an example of a dark frame that must be subtracted from each image. This is a "sigma" combine of 6 five minute dark images with the camera at -40C. A "sigma" combine is an average of all non-outlier pixels. If a single pixel in one of the images is very far from the average of the other images, typically because of a cosmic ray strike, that pixel is not included in the average.
Date: October 2009
Camera: SBIG ST-10XE
Processing Notes: Capture with CCDSoft. Combined with Sigma Beta.