[daip] aips help ...

[Eric Greisen]

Dharam Vir Lal wrote:
> Dear Eric,
> 
> I have a few (X-ray/Chandra) FITS images (say 4) and I have loaded them in
> to AIPS using IMLOD.  I have named them in SEQuence with identical map
> names (1.IMAP.1, 1.IMAP.2, 1.IMAP.3 and 1.IMAP.4) and I want to use AIPS
> task FLATN to stitch these images.  Since, there is obviously no
> "frequency axis", the FLATN task dies with an error "FREQ AXIS FOR PRIMARY
> BEAM CORRECTION" and gives an output image-file with just the first image.
> 
> Any suggestion, how I can get around this problem?  Basically, I want to
> stitch a few FITS images using AIPS task FLATN.

I think you are using the 4 images as pointings - when they are combined 
in radio data it is necessary to correct for primary beams since radio 
images are images of the sky multiplied by a primary beam.  If the 4 
images were treated as fields of 1 pointing, then the primary beam 
correction is not made.  The images then would need names with the same 
seq number and class names such as IMG001, IMG002, IMG003, and IMG004.
See how that goes...

Eric Greisen