Find USNO sources located within the FoV of an image that has a valid WCS installed inthe header.

% cdfp_sky2xy --help    
Usage: cdfp_sky2xy 20170903T034319.0_acm_sci.fits  usno_all.cdfp 
arg1 - name of FITS image with WCS installed 
arg2 - name of the cdfp file giving Ra,Dec 

cdfp_sky2xy:
  A routine that takes and image and a cdfp catalog as input. The 
Ra,Dec of all targets in the csfp file are extracted and processed 
with the wcstoolsroutine sky2xy using the input FITS image (that must 
have WCS in the header). The resulting list is processed to create a 
file of Xpix,Ypix,iflag. The (Xpix,Ypix) values give the predicted 
image location (in pixels) on the image, and the iflag (integer) value 
indicates whether the target is on the image (iflag=1) or out of the 
image FoV (iflag=0).