Here are the IRAF screens, as well as I can reconstruct them from memory, that I showed in beginning to introduce the topic of noise in CCD images on 27 August 2008. The bias frames I used for the demonstration were made in 2005 with the older CCD camera (named CCD1) that I used for show and tell in that class.

The first screen shows the second bias image displayed with the X application ds9.

Here is a plot of a single column (column 429) of the first bias frame. You can tell that it's a column because the x axis comprises 1200 pixels, which is the length of the readout direction for this CCD.
The next three images show a small region of the bias frames, with one, two, and three of them overplotted (respectively).
Page last updated 8/28/08 by Nancy Morrison.