[daip] New Staff Reply - [!IRD-375367]: Beam (PSF) measurement

[Eric Greisen]

New Staff Reply: Beam (PSF) measurement

Not with any exactness - a rough beam size can be found by 1/max baseline
in radians.  There are a bunch of adverbs in IMAGR all of which can
change the resulting beam size.  Things like natural vs uniform weighting
affect it a lot (natural emphasizes short spacings heavily).  The degree 
of uniform weighting (ROBUST adverb), whether uniform weighting is done
over a single cell or multiple cells (UVSIZE, UVBOX, UVBXFN), and whether
the data are averaged in time over baseline-length dependent intervals
(IM2PARM(11,12,13)) all change the synthesized beam width by factors of
2 or more.  The UVTAPER is also important.

Note that the beam size has only to do with the weighting and distribution
of the data samples and so does not depend (much) on data calibration.

Eric Greisen


Ticket Details
===================
Ticket ID: IRD-375367
Department: AIPS Data Processing
Priority: Default
Status: Closed
Link:  https://help.nrao.edu/staff/index.php?_m=tickets&_a=viewticket&ticketid=1677