AIPS HELP file for STEER in 31DEC24
As of Thu Apr 25 6:20:09 2024
STEER: Task which deconvolves the David Steer way.
INPUTS
Dirty image
INNAME Image name (name)
INCLASS Image name (class)
INSEQ 0.0 9999.0 Image name (seq. #)
INDISK 0.0 4.0 Image disk drive #
Beam image
IN2NAME Image name (name)
IN2CLASS Image name (class)
IN2SEQ 0.0 9999.0 Image name (seq. #)
IN2DISK 0.0 4.0 Image disk drive #
Steer image
OUTNAME Image name (name)
OUTCLASS Image name (class)
OUTSEQ -1.0 9999.0 Image name (seq. #)
OUTDISK 0.0 4.0 Image disk drive #
GAIN -1.0 1.0 Steer loop gain
NITER 0.0 32767.0 Maximum # of iterations
DOTV -1.0 1.0 TV display of residuals?
NBOXES 0.0 10.0 Number of boxes
BOX 0.0 4096.0 Four coordinates for each box
BADDISK -1.0 1000.0 Disks to avoid for scratch.
OFFSET -1.0 1000.0 Trim level
HELP SECTION
STEER
Type: Task
Use: STEER deconvolves the dirty beam from the dirty map thus
producing a map with the units of brightness (Jy/pixel).
Conversion to other units e.g. KELVIN can be done with AXDEFINE.
STEER may be restarted if further improvement is desired. This
program is slow but should be comparable to APCLN if the map
contains many picture elements. The task CONVL may be used to
convolve the map to the resolution produced by a CLEAN program.
The algorithm used in the program is due to David Steer.
The principle is similar to Barry Clark's CLEAN except that in
the minor cycle only points above the (trim level)*(peak in
the residual map) are selected. In the major cycle these are
removed using an FFT. If the BOXes are chosen to surround the
source snugly then the algorithm will converge faster and will
have more chance of finding a unique image.
This is an experimental program; please relay any
complaints etc. to Tim Cornwell at the VLA
Adverbs:
INNAME......The dirty image name. Standard defaults.
INCLASS.....The dirty image class. Standard defaults.
INSEQ.......The dirty image seq. #. 0 => highest.
INDISK......The dirty image disk drive #. 0 => any
IN2NAME.....The beam image name. blank => actual
INNAME, otherwise standard defaults.
IN2CLASS....The beam image class. Standard defaults
except blank => 'RBEM' if INCLASS = 'RMAP'
'LBEM' if INCLASS = 'LMAP'
'IBEM' if INCLASS = anything else
IN2SEQ......The beam image seq . #. 0 => actual INSEQ
IN2DISK.....The beam image disk drive #. 0 => any
OUTNAME.....The Steer image name. blank => Standard defaults
based on INNAME.
OUTCLASS....The Steer image class. Standard behavior with
default = 'XGS ' if INCLASS = 'XMAP'
OUTSEQ......The Steer image seq. #. 0 => highest unique
If >0; image will be created if new,
overwritten if image name exists.
OUTDISK.....The Steer disk drive no. 0 => highest with space
GAIN........The Steer loop gain. 0 => 0.01, for most cases
0.02 will work well.
NITER.......Steer iteration limit. 0 => 20
DOTV........Display Steer map on TV channel 1. > 0 => yes.
If true, you may stop the Steering with TV button
D after each Steer map is displayed.
NBOXES......The number of rectangular boxes. The Steer image
is non-zero only within these boxes. 0=>1
BOX.........A 4x10 array with the BLC and TRC of each box.
0 => use inner quarter of input map (first box)
0 => ignore box (boxes 2 - 10)
BADDISK.....This array contains the numbers of disks on which
it is desired that scratch files not be located.
BADDISK has no effect on input and output maps.
OFFSET......The Trim Level. In a minor cycle only points
above this fraction of the peak residual are
selected. 0.8 works well.
EXPLAIN SECTION