Append columns to table, while preserving header

Question

I am trying to update a FITS table extension by appending some new columns to it. I am following the method given at http://pyfits.readthedocs.org/en/latest/users_guide/users_table.html#merging-tables. However, the header of the merged table contains only the bare minimum information required to identify the column. There was information in the original header file that I need. How can I carry all the extra keywords from the old table across to the new one?

I have already tried

merged_table.header = old_table.header

and adding in the necessary entries for the new columns manually, but this always corrupts the header and makes the entire FITS file unreadable.

Thanks

Answer 1

The best answer to this partly depends on how the new table is being created, but as of the latest version of PyFITS (v3.3.0) or Astropy (v0.4.2) the BinTableHDU.from_columns method, which creates a new BINARY table HDU from a set of column definitions accepts an optional header argument which can receive, for example, the header from the original table HDU.

This will ignore any keywords related to the table structure as understood by the FITS format, and only keep other metadata. I believe there was a bug for a bit where the header argument was ignored but that should be fixed now.