[daip] Help with AIPS CC files

[Jose Afonso]

Dear Eric,
I need to modify my AIPS CC files in a peculiar way, and I wonder if there is an easy route to do it.

The data is from GMRT, taken during a period when there was a timestamp issue (timestamp at the beginning of the integration instead of the middle, or the other way around, can't remember exactly but I think that's ok). The result is that the sources in the resulting image are shifted by some amount in RA and DEC (which I can either calculate, if I go and precisely get what the timestamp problem was, or I can just compare with a more recent map with accurate positions and get a observed deltaRA and deltaDEC). 

I need to use the CC files resulting from the old data (with the RA,DEC shift) as input model for the self-cal of the new data, so I need to change the CC  components adding a given deltaRA and deltaDEC. I would think there is an easy way to do this, as long as you know the structure of the CC files (which I don't, I'm afraid). Could you help me with this? Is there an easy way to just add this deltaRA, deltaDEC to all CCs? Even exporting to an ascii table, modifying it, and re-importing, or something? I'm not sure if this matters, but although the old and new images are from the same region, the pointing is slightly different - which would result in an extra headache in case the CCs are stored in pixels relative to the tangent point I would guess...

Many thanks for whatever help you can provide.
Jose

Jose Manuel Afonso
Observatorio Astronomico de Lisboa
Tapada da Ajuda, 1349-018 Lisboa
Tel: +351 21 361 67 45/30 Fax: +351 21 361 67 52
Email: jafonso at oal.ul.pt
Webpage: http://www.oal.ul.pt/~jafonso