Incorrect phaseshifting from NCP to another position
Created by: tikk3r
We just encountered this while working on an NCP dataset. Shifiting from the pole to another position gives problems. After shifting, all the headers indicate the right position: msoverview reports the location given to the phaseshift and FITS images have the right coordinates in their headers. However, the data is (in this case) 180 degrees off in right ascension.
The data was phase-shifted from RA=00:00:00.000000 DEC=+90.00.00.00000 to RA=13:15:57.040099 DEC=+89.29.08.61202, however, physically the data is 180 degrees off and represents the field located at RA=1:15:57.040099 DEC=+89.29.08.61202.
This is the image of the phase shifted data (left), compared to an image of the source in the NCP field that should be there:
This is the image of the phase shifted data, with the RA in the FITS header modified by 180 degrees (right) compared to the corresponding location in the NCP field:
Pretty much everything except the bright source in the first image is more or less subtracted from the field, hence the low flux level, but it demonstrates the problem. I guess this has something to do with right ascension being undefined or degenerate at the pole?
Frits