The TV command writes the image array to the display without scaling it. Before reduction of data can take place the calibration images must be dealt with properly. This new image, with every pixel value a median of all of the input frames, is the output. The main purpose for using this process of the removal of spurious high and low points that effectively reduces noise and therefore, the uncertainty. Both biases and dark frames can be medianed easily using this routine.
Flat fields are slightly more complicated.
The flat field frames for a specific filter should be medianed together after which the medianed bias and dark frames should be removed. Flat fields must also be normalized. This is accomplished by weighing the medianed frames to the average value. To do this, set the scale to 1 when running the procedure. When this has been done for all filters, the reduction is almost complete.