[daip] help with AIPS

[Eric Greisen]

Melanie Gendre wrote:
> Hi,
> 
> My name is Melanie and I am having some trouble with AIPS.
> I have data at 90cm, with 150 sources detected in 2 pointings of the VLA
> (BnA and CnB configurations). I need to get contour plots of the sources
> and estimate their 90cm flux.
> I am familiar with data reduction for one source per pointing, making low
> resolution images at higher frequencies. It is my first time with multiple
> sources per pointing though.
> 
> As far as I understand, the calibration process for multiple fields is
> similar to single field calibration. I use the standard procedure:
> FILLM, LISTR, QUACK, SETJY, CALIB, EDITA, GETJY, EXTDEST, CLCAL, SNPLT,
> SPLIT, UVSRT
> 
> After that, I am a bit lost. I see that we can get recommendation for each
> field size with SETFC and then use IMAGR to clean and make the image, but
> I am a bit fuzzy on the details, especially the use of BOXFILE. So here
> are my questions:
> - What is the format for BOXFILE if I want to use it in SETFC and IMAGR?
> It is a different format that the BOXFILE use in the CLEAN section of the
> cookbook as I have to specify FLDSIZ, RASHIFT and DECSHIFT...
> - What tasks should I then use to get images and flux of my separate sources?

There is only one BOXFILE format used by all aips tasks.  SETFC will, if 
you set CELLSIZE and IMSIZE to 0.0, recommend a cell size and image 
size.  The latter will be a correct power of 2 but the former will be 
some odd number.  I recommend deleting the boxfile written by that 
SETFC, and then changing the CELLSIZE returns by SETFC to a nearby 
rounder number.  Then run SETFC again.  This will write a BOXFILE with 
all of the fields (facets) specified with center RA and Dec and with 
default Clean boxes - large circles that avoid the edges and esp corners 
of the image.  You can use the TV during IMAGR to change these boxes. 
With SETFC and a BOXFILE (and use OBOXFILE too in IMAGR to capture the 
boxes you set with the TV) there is no need to specify the adverbs 
RASHIFT, DECSHIFT, FLDSIZE, NBOXES, CLBOX.  If you already know that 
there are 150 sources, I would think that you must already have run IMAGR??

After the imaging and self-cal are done, use FLATN to make one large 
image of all the facets.  Then SAD or JMFIT can be used to fit the flux 
and size of the sources - the former will find them and try to fit them 
but will omit those it has trouble with and so is incomplete.  The 
latter has to be pointed by hand at each source individually.  If a 
source is an extended mess rather than a clean Gaussian, use TVSTAT or 
IMSTAT carefully to estimate its flux.

Eric Greisen