Use graphical tools to confirm that an image has a valid WCS in the FITS header. Collect an expanded set of targets from the USNO-B1.0 catalog and derive an improved WCS solution. The user is given the choice of two types of solution (2lin for use with lots of stars, and trs for use with just a few stars).

% wcsf_final --help 
Usage: wcsf_final list.0 Y N 
arg1 - Name of file with list of FITS images (can be full path)
arg2 - Build a new USNO catalog (Y/N)
arg3 - run in debug mode (Y/N)

The input image and the initial detection catalog are taken from the IMGCAT0 archive. The user may elect to build a fresh CDFP catalog of USNO-B1.0 sources, or a pre-existing version from the VISCAT archive is extracted. The normal reduction sequence is: 1) The image and USNO catalogs are cross-matched. 2) The cross-matched sources are used to establish Ra,Dec,X,Y values 3) A WCS is computed using a user-specified method 4) Any discrepant residuals are elimiated and the user van return to #3 5) The image with the final WCS is written to the WCS archiv.

The second argument (arg2) could use a few more words. If the value assigned is "Y", then the user is given the choice of using repeated calls to a code that compiles a set of USNO-B1.0 sources. The user can specify selection by the USNO Blue or Red magnitudes, and different faint selection limits can be used. This is quite convenient with most images. If the value assigned to arg2 is "N", then the CDFP catalog already in the ./local_red/VISCAT subdirectory will be used. You can read some more about this latter choice in wcsf_viscat.

There are some useful sanity checks you can run after executing wcsf_final. Here are a couple:

You can overplot USNO sources on one the newly calibrated image: 
  % mli_copy ./local_red/WCS/20190217T122456.6_acm_sci.fits  
  % usno_look_wcs_run 20190217T122456.6_acm_sci.fits N 
This will leave local versions of the image, the cdfp fle and a png
image of the final set of USNO-B1.0 stars in the field. 

Just inspect the end of the header file: 
  % imhead 20190217T122456.6_acm_sci.fits  
CROTA2  =     128.469299316406 / Image Twist +AXIS2 W of N, (deg)
CDELT1  =      0.0000753402855 / Axis 1 Pixel Size (degs)
CDELT2  =      0.0000753402855 / Axis 2 Pixel Size (degs)
RMSRA   =               0.3280 / RA_rms in arcsec
RMSDEC  =               0.3550 / DEC_rms in arcsec
NUMWCS  =                   20 / Number of points in WCS fit

The last three numbers show you the RMS of the fit residuals and the 
number of calibrating stars used.