Sky Flats

A sky-flat image is generated from all-sky imaging data, typically in conjunction with the building of a pointing model as in Section 5.4. A typical sky-flat, as shown in Figure 7.2, is a convolution of the ``real'' twilight flat with a fringing pattern, described in Section 7.3.3.

Figure 7.2: A sample sky flat. The fringe pattern from the night sky lines is clearly evident.