ucac4.py

The recommended source of reference stars for astrometry measurements is UCAC4 (Fourth US Naval Observatory CCD Astrograph Catalog), see Zacharias et al. 2013. The UCAC4 catalog can be queried at Vizier and a local copy is available on the Astrolab File Server.

To obtain astrometric measurements linked to the UCAC4 catalog for a FITS image, run the ucac4.py python script.

If the header of the input FITS contains the field centre, i.e. RA, DEC keywords, and TELESCOP keyword then

python /mnt/64bin/auto_astrom/ucac4.py fits_image

A new FITS image with the UCAC4 astrometry mapping is produced, i.e. "a"+fits_image, and a file listing non-UCAC4 catalog objects found in the image, i.e. fits_image+"_astrom_new", is produced.

If the field centre is unavailable, e.g. on older images in the archive, then a rough (RA, Dec) centre and pixel scale is needed by the script.

python /mnt/64bin/auto_astrom/ucac4.py fits_image ra_cen_deg dec_cen_deg pixel_scale

where ra_cen_deg and dec_cen_deg define the field centre in degrees and pixel_scale is pixel scale in arcsec per pixel.

The find_jpl_position.py script can be used to find a position of asteroid when the field centre is not given in the FITS header.

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jrl

2020-Jun-17 12:43:38 UTC