Note: The program must be run under X-windows as graphics are displayed.
The first things the script does is to display the middle focus image on the screen. It then asks you to select a nicely exposed isolated star in the field to use as the focus star.
Once done it displays a montage of the focus images. On
focanl determines the best focus by first creating a table of focus_position and second moments. It does this by inspecting each image and doing the following:
Once the table is created it fits a parabola and determines the minimum focal position. The minimum should appear as a circle.
