Re: Data sets over time

[Stupendous Man <richmond@stupendous.cis.rit.edu>]

  Rob asked:

> Are the headers updated after the reductions are done, or are the headers
> real, real accurate? 

  From http://spiff.rit.edu/tass/pipeline/pipeline-latest/pipeline.html

        For every image which matches the reference catalog, 
        the pipeline will write new, more accurate values for 
        the RA and Dec of each field center into the make_list.out file. 
        The pipeline will also modify the cleaned image's FITS header 
        in the following way:

             * CRVAL1 will be set to the newly determined Dec value 
                         (decimal degrees)
             * CRVAL2 will be set to the newly determined RA value 
                         (decimal degrees)
             * CRPIX1 will be set to the pixel coordinate of the 
                         column used as the Dec field center (which is 
                         the axis_colpos parameter in the astrom.param file)
             * CRPIX2 will be set to the pixel coordinate of the row 
                         used as the RA field center (which is 
                         the axis_rowpos parameter in the astrom.param file) 


  So the pipeline updates the position values in the FITS headers
of images as it reduces them.  Note that this information is 
_also_ available in the "make_list.out" file, which is a single
small ASCII text file produced by the pipeline.  Perhaps having
the "make_list.out" files for a large number of nights might be
more compact, and nearly as informative in some ways, as having
all the FITS images themselves.

                                                    Michael Richmond