quick_beam_fit - gaussian model fitter

This program performs an elliptical gaussian fit to the signal in planet map(s). The output can be analyzed to assess focus quality.

Analyze maps

Use a parameters file like quick_beam.in. The list of maps to analyze can be passed in on the command line, or specified in a file.

quick_beam_fit quick_beam.in

Output looks like:

#             peak_x  peak_y   peak_h  fwhm_a  fwhm_b   angle  baseline    noise
source1.fits  0.0001  0.0001   0.2730  0.0234  0.0213  117.38  8.161e-04 5.492e-04
source2.fits -0.0013 -0.0027   0.2700  0.0234  0.0215  116.85  8.004e-04 5.425e-04

The position of the peak in the map is given, in degrees, by peak_x and peak_y. The major and minor FWHM of the gaussian model are fwhm_a and fwhm_b, in degrees. The orientation of the major axis, measured in degrees from X towards Y, is angle. The baseline and noise indicate the approximate mean map level and white noise level, respectively.

The code also creates plots with annotations. The plotting can be configured to some extent, to change the zoom factor or set linear / log color scale.

Focus assessment

If evaluating beam quality in a planetfest situation, the product of the major and minor FWHM gives a good proxy for beam solid angle (especially if you scale it by pi/2). In the plots, this number is labeled “Omega_G”. The peak amplitude is another useful indicator of beam quality.