Usage

focanl fits_files ...

focanl inspects the FITS files in the argument and determines the best focus. The fits_files should be generated by the focusdip (Section 5.4.3) command.

Figure 5.1: A montage of twenty typical focus images as produced by focusdip.

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:

• reading the header for the TELFOCUS
• determining the sky (Section 5.4.6 for each image
• determining the second moment after removing sky using XVista centroid command

Once the table is created, it fits a parabola using linfit (Section 5.10.4) and determines the minimum focal position. An example is given in Figure 5.2

Figure 5.2: The parabolic fit to a set of focus values as found by focanl