The results, in the
above table, are for a single field-of-view and do not suggest that
one software package is better than another. Additional FOVs showed
that the results vary greatly.
The Star Count column indicates the number of identified useful
stars by eXcalibrator for color
balancing. The data show that the major factor in star count is the
accuracy of the Position Angle.
With the above data,
eXcalibrator calculated identical color balance ratios in all five
The table also shows that using the Astrometry.net default settings
can produce inferior results. The declination is off by one
arc-second with a significant error in the PA. Additional tests show
that it is better to select the
Source Extractor option on the Astrometry.net upload page. The
results can be significantly improved but never reduced.