Program: PBCORR
Purpose: Corrects maps for primary beam correction
Category: MANIPULATION
File: pbcorr.shl
Author: M. Vogelaar
Keywords:
INSET= Input set (and subsets). Maximum number of subsets
is 2048.
BOX= Frame for input subsets. [entire subset]
OUTSET= Output set and subset(s) for the result. The number
of output subsets is the same as the number of input
subsets.
POS= Coordinates for which user wants [stop]
to know the primary beam correction. This keyword
is asked only if MANUAL=Y is specified. Maximum
number of coordinate pairs is 64.
*** BACK= If user selects 'N' (default), a primary [N]
beam correction is applied. If 'Y' is selected, an
attenuation is applied to your maps.
*** MANUAL= If user wants to apply correction [N]
(or attenuation) on single points, select 'Y'.
End the session by pressing .
*** OPTION= Give cutoff behaviour: 1/2/3/[4]
For the manual mode only option 1 applies. The option
cannot be changed in that case.
FREQUENCY= Give frequency: [1.415 GHZ]
If PBCORR cannot find a proper frequency,
the frequency is asked with FREQUENCY= The keyword
accepts a number and a unit. If no unit is given, the
number is in Ghz. Otherwise, a conversion is done to Ghz.
The possible units to convert from are for example MHz,
Hz, but also cm (all upper- or lowercase). The keyword
is asked unhidden only once.
Description: PBCORR corrects an image for the primary beam effects of
WSRT, VLA (VLAP), ATCA (Australia Telescope Compact Array)
FST antennas and the millimeter arrays IRAM-PdB, NMA
(Nobeyama), OVRO and BIMA. The correction is proportional
to the square of the distance from the pointing position.
The coordinates of the pointing position are taken from
the header (items PCRA and PCDEC, values in degrees). If
these descriptors cannot be found, the physical values of
(pixel) position (0,0) is substituted and the user is
warned. There is a cutoff in the distance:
Outside the validity range, the correction is set to a
value depending on OPTION= For WSRT and VLA The cutoff
occurs at a primary beam sensitivity of 2.3% of the value
at the beam center, i.e. where the Antenna Power Spectrum
is equal to 2.3/100. For the Fleurs telescope the cutoff
is (at 21 cm) at a distance of 2.8 degrees.
For the ATCA the cutoff occurs for RF = 50 arcmin GHz in
all bands.
Possible values for OPTION=
OPTION=1 : Return 0 if beyond cutoff, i.e. do
not correct image values beyond cutoff.
OPTION=2 : Return min. allowed correction beyond
cutoff. The function calculates
this value for different telescopes.
OPTION=3 : Disable cutoff, i.e. return values
that correspond to coordinates
outside the validity range of the
correction function.
OPTION=4 : Return blank if beyond cutoff.
Notes: The correction formulas are described in pribeam.dc1
Updates: Mar 2, 1990: MV, Document created.
Apr 8, 1992: MV, OPTION= included.
Jul 24, 1992: MV, Document changed for new pribeam routine.
Jun 9, 1993: MV, Document changed for new pribeam routine.
(Millimeter arrays, Australia Telescope)