AIPS HELP file for OBITPEEL in 31DEC24
As of Sat Oct 5 15:48:23 2024
OBITPEEL: Make/Clean/Self-cal/Peel images with OBIT task Imager
INPUTS
DOWAIT -1.0 3.0 > wait for and display output
DOCRT -4.0 132.0 > 0 display output on
terminal, else message file
OBITVERS 0.0 =2 for python2, else 3
INNAME Input UV data (name)
INCLASS Input UV data (class)
INSEQ Input UV data (seq. #)
INDISK Input UV data disk drive #
SOURCES Source name
QUAL -10.0 Calibrator qualifier -1=>all
CALCODE Calibrator code ' '=>all
TIMERANG Time range to use
FREQID Freq. ID to select.
SUBARRAY 0.0 1000.0 Sub-array, 0=>all
DOCALIB -1.0 101.0 > 0 calibrate data & weights
> 99 do NOT calibrate weights
GAINUSE CL (or SN) table to apply
DOPOL -1.0 10.0 If >0.5 correct polarization.
FLAGVER Flag table version
DOBAND -1.0 10.0 If >0.5 apply bandpass cal.
Method used depends on value
of DOBAND (see HELP file).
BPVER Bandpass table version
STOKES Desired Stokes: I, Q, U, or V
BCHAN 0.0 8192.0 Low freq. channel 0 for cont.
ECHAN 0.0 8192.0 Highest freq channel
NCHAV Number of chan. to average.
CHINC Channel incr. between maps.
BIF First IF in average.
EIF Last IF in average.
OUTNAME end of output image name
OUTSEQ -1.0 9999.0 Output seq. no.
OUTDISK Output image disk drive #
DO3DIMAG -1.0 1. > 0 => use different tangent
points for each field
FOV 1.E-6 Radius of the desired field
of view (in degrees)
CELLSIZE 0.0 (X,Y) size of grid in asec
UVTAPER 0. (U,V) Gaussian taper
units are kilo-lambda
ROBUST Robustness power: -5 -> pure
uniform weights, 5 => natural
NITER 0.0 Maximum # of Clean components
FLUX Stop Clean when max residual
< FLUX
IMAGRPRM (1) > 0 => correct primary
beam freq dependence
(2) correct data by this
spectral index
(3) Min flux to invoke source
auto centering (Jy) 0->no
(11) Multi-scale bias
(12) Multi-scale SNR factor
(13) Multi-scale Qual factor
IM2PARM (1) > 0 => automatically find
Clean boxes - do this!
(2) max outlier distance deg
(3) min outlier flux (Jy)
(4) outlier spectral index
0 -> -0.7.
(5) Baseline-dependent time
averaging factor
(6) BL time averaging FOV
(11) max Phase SC loops
(12) min Flux for Phase SC
(13) Phase SC solint (min)
(14) max A&P SC loops
(15) min flux for A&P SC
(16) A&P SC solint (min)
(17) min S/N ratio in SC
(18) min number antennas SC
(19) do Mean gain constraint
(20) no negative CCs
(21) max loops in Peeling
(22) min flux to do a Peel
(23) Peel reference antenna
(24) min SNR allowed in Peel
(25) Peel solution interval
(26) min Clean flux in Peel
(27) max # CCs in Peel
(28) > 0 -> A&P in Peel
(29) > 0 -> L1 in Peel
REFANT Reference antenna
SOLTYPE Solutionn type,' ','L1'
WTUV Weight outside UVRANGE 0=,01
NGAUSS 0.0 10.0 Number of scales to use
not incl the un-tapered one
WGAUSS 0.0 Scales as x-pixel tapers
not incl the un-tapered one
MAXPIXEL 0.0 999999.0 Maximum pixels searched in
each major cycle.
PRTLEV -1.0 5.0 Amount of messages desired:
0 -> 2.
DOTV -1.0 512.0 Display residuals on OBIT TV
NTHREAD 1.0 Maximum number threads to use
BADDISK -1.0 1000.0 Disks to avoid for scratch.
HELP SECTION
OBITPEEL
Type: "Verb"
Use: The OBIT package of astronomy software written by Bill Cotton
of NRAO Charlottesville is available at some institutions. If
it is available and in your $PATH, then you may use this verb
to run a slightly simplified version of the OBIT imaging task
Imager. It does not offer SDI Clean and several lesser options
of Imager. It does a multi-facet image with data calibration
and selection options covering a selected field of view fully
including outlying facets on strong NVSS sources. Self-cal and
peeling options are also offered. Multi-scale Clean is offered
as is baseline-length dependent time averaging to reduce the
size of the work file. The facets are "flattened" into a
single output image when DO3D is false. The Clean components
are retained with the facets or the flattened image and may be
used for self-cal.
The log and run file for each execution of OBITPEEL will appear
in your $HOME area. The UV work file will appear on OUTDISK,
named with the source name, a class of 'Imager', and a new
higher sequence number. This file contains 'SN' extension
files needed to apply the calibration found by OBITPEEL.
The input adverbs are saved with a TPUT equivalent when this
verb is invoked.
The Explain file attached contains the full help file for
Imager.
Either phase only or amplitude and phase or both types of
self-calibration can be performed. If both are done, then
phase calibration is done first and applied to the data before
Amp & Phase self-calibration. In any case, there will be an
SN table attached to the output uv data which is needed to
fully calibrate it.
Peeling is the procedure of doing a self calibration on a
single source, removing it and reverting to the previous
calibration. This is useful for a very strong source whose
artifacts disturb the other parts of the field. If the maximum
pixel value in any image (as defined by the CLEAN components)
exceeds IM2PARM(22), then the facet in which the maximum value
occured is peeled. This procedure is iterated until no facet
has a pixel in excess of IM2PARM(22).
NB: peeling of many sources will likely degrade the results.
It is strongly recommended that IMAGRPRM(3) be no larger than
IM2PARM(22) so that the source is properly centered in its
facet.
Adverbs:
DOWAIT.....A log file is written into your $HOME area from the obit
task. If DOWAIT <= 0.0, AIPS does not wait for the OBIT
task Imager and you will need to look at the log file
with more, less, cat, or an editor. If 0 < DOWAIT < 2,
the messages from Imager will appear as the OBIT task
generates them. If DOWAIT >= 2, AIPS will wait for
Imager to finish and then echo the log file under control
of DOCRT.
DOCRT......> 0 Use the terminal, the full length of the log file
lines will appear so widen it at least a little.
<= 0 Write log file to message file at level 0 (no echo
to the terminal). Some messages may get truncated.
DOCRT is not used when DOWAIT < 2.
OBITVERS...OBIT now is designed to run on python 3 or 2.7. If you
have a newer version of OBIT (post 01-Apr-2021) then you
may want the python3 version which is now the default.
If you need the older version, set OBITVERS=2.
INNAME.....Input UV data file (name). Standard defaults.
INCLASS....Input UV data file (class). Standard defaults.
INSEQ......Input UV data file (seq. #). 0 => highest.
INDISK.....Input UV data file disk drive #. 0 => any.
SOURCES....Source name - specify up to 30 sources to be processed
sequentially.
QUAL.......Only sources with a source qualifier number in the SU table
matching QUAL will be used if QUAL is not -1.
CALCODE....Sources may be selected on the basis of the calibrator code
given in the SU table.
' ' => any calibrator code selected
'* ' => any non blank code (cal. only)
'-CAL' => blank codes only (no calibrators)
anything else = calibrator code to select.
NB: The CALCODE test is applied in addition to the other
tests, i.e. SOURCES and QUAL, in the selection of sources
to process.
TIMERANG...Time range of the data to be copied. In order: Start day,
hour, min. sec, end day, hour, min. sec. Days relative to
ref. date.
FREQID.....Frequency identifier to select (you may determine which is
applicable from the OPTYPE='SCAN' listing produced by
LISTR).
SUBARRAY...Sub-array number to copy. 0=>all.
DOCALIB....If >= 1, calibrate the data using information in the
specified Cal (CL) table for multi-source or SN table for
single-source data. If >= 2, calibrate the weights.
THIS IS DIFFERENT FROM NORMAL AIPS USAGE - BE ESPECIALLY
CAREFUL WITH EVLA DATA and apply cal to weights only
after REWAY or TYAPL.
GAINUSE....version number of the CL table to apply to multi-source
files or the SN table for single source files.
0 => highest.
DOPOL......If > 0.5 then correct data for instrumental polarization
as represented in the AN or PD table. This correction is
only useful if PCAL has been run or feed polarization
parameters have been otherwise obtained. See HELP DOPOL
for available correction modes: 1 is normal, 2 and 3 are
for VLBI. 1-3 use a PD table if available; 6, 7, 8 are
the same but use the AN (continuum solution) even if a PD
table is present.
FLAGVER....specifies the version of the flagging table to be applied.
0 => highest numbered table.
<0 => no flagging to be applied.
DOBAND.....If true (>0) then correct the data for the shape of the
antenna bandpasses using the BP table specified by BPVER.
The correction has five modes:
(a) if DOBAND=1 all entries for an antenna in the table
are averaged together before correcting the data.
(b) if DOBAND=2 the entry nearest in time (including
solution weights) is used to correct the data.
(c) if DOBAND=3 the table entries are interpolated in
time (using solution weights) and the data are then
corrected.
(d) if DOBAND=4 the entry nearest in time (ignoring
solution weights) is used to correct the data.
(e) if DOBAND=5 the table entries are interpolated in
time (ignoring solution weights) and the data are then
corrected.
IMAGR uses DOBAND as the nearest integer; 0.1 is therefore
"false".
BPVER......Specifies the version of the BP table to be applied
0 => highest numbered table.
<0 => no bandpass correction to be applied.
BCHAN......First channel number to image, 0=>1. Channel numbers are 1
relative as defined in the input data file.
ECHAN......Highest channel number to to include in image,
0 => max The actual # of output channels will be
(BCHAN-ECHAN+1-NCHAV)/CHINC + 1
Thus, ECHAN is the highest channel in the input averaged
into the output and is the highest output channel only if
NCHAV and CHINC are 1.
NCHAV......NCHAV is the number of channels to be averaged together
in in the gridding process. 0 => 1. If this value is less
than the total number of channels, then a multi-channel
image will result.
CHINC......Number of input channels to skip between images. 0 => 1
BIF........The lowest numbered IF to include. Multiple IFs can be
included in a bandwidth synthesis average. 0 => 1.
EIF........The highest numbered IF to include. 0 =>highest.
Note: not all data sets will have IFs.
OUTNAME....The output image name will be the source name + Stokes +
the contents of OUTNAME in that order.
OUTSEQ.....Output sequence number. 0 => highest to produce unique maps
and beam. Note that this will produce, potentially, maps
and beams with a variety of sequence numbers depending on
what files are already on disk. If OUTSEQ > 0, all images
and beams for all fields are assigned that sequence number
and pre-existing files are reused. An error will occur if
the pre-exsitng files are of different sizes than the ones
currently being requested.
OUTDISK....The disk drive # of output images. 0 => highest with space
Image and Beam go on same disk. Note: OUTCLASS='xCLnnn'
where x=Stokes, nnn=field number and 'xBMnnn' is the beam
CLASS. If NITER=0, OUTCLASS='xIMnnn'
DO3DIMAG...> 0 => make the images by shifting the tangent point to the
field center. This may be more accurate for significant
shifts than the u,v modification done with DO3D false
which is called by some "faceting in the uv plane".
With DO3D > 0, the facets are left as individual images
on disk, while with DO3D <= 0, the facets are flatened
into one large image (with CC data) and then deleted.
FOV........Radius of the field-of-view to be imaged in degrees.
NO DEFAULT.
CELLSIZE...(X,Y) pixel separation in asec. 0,0 => let Imager
choose which is a reasonable option. Imager will choose
the IMSIZE for you in any case.
UVTAPER....(U,V) Gaussian taper (kilo-lambda) at 30 percent level
0,0 => no taper.
ROBUST.....Briggs' "robustness" parameter. "Uniform" weights are
tempered by a constant being added to the local density of
weights. ROBUST = -4 is nearly pure uniform weighting,
ROBUST = +4 is nearly pure natural weighting. Use of this
option requires a second array in the "AP" memory and may
therefore force the data to be sorted. The option is
turned off if ROBUST < -7 and uniform weighting is turned
off is ROBUST > 7. See HELP ROBUST - the AIPS ROBUST
differs numerically from that of Briggs.
NITER......Clean iteration limit. 0 => no Cleaning.
FLUX.......Stop Clean when abs(resid. image max) < FLUX (Jy) If FLUX
< 0 then Clean stops at first negative Clean Component.
IMAGRPRM...NOTE: these are similar in usage to --- BUT NOT THE SAME
--- as in IMAGR
(1) If > 0 then make frequency dependent primary beam
corrections assuming an antenna diameter of IMAGRPRM(1)
meters.
(2) Visibility amplitudes will be corrected to the average
frequency assuming a spectral index of IMAGRPRM(2).
Note: the typical optically thin synchrotron spectral
index is about -0.7.
(3) If > 0, do auto centering of all sources for which
the sum of the clean components within 1.5 pixels of
any pixel exceeds IMAGRPRM(3) and for which the
centroid is not within 0.05 of a cell of a pixel then
the image is remade and deconcolved with the bright
sources (>IMAGRPRM(3), one per facet) on a pixel. This
is necessary to achieve high dynamic range. If the
initial dirty image has a pixel brighter than
IMAGRPRM(3), then it presumes that the final image will
need centering and the initial CLEAN is stopped at
minFlux = 0.1 * IMAGRPRM(3).
(4)-(10) not used at present
(11) If NGAUSS > 0, multi-scale Cleaning will be done.
IMAGRPRM(11) is a bias toward higher resolution.
0 -> 0.2 As the CLEAN progresses, this factor is
reduced by (1-iteration/niter)**3
(12) Multi-scale SNR factor 0 -> 0.35
(13) Multi-scale "quality" factor. 0 -> 0.2
The objective function used to chose the resolution
for the next major cycle is evaluated on the facet
at each resolution with the highest "quality" and is
given by:
fact1 * (maxTaper - Taper)/maxTaper +
fact2 * (resid_peak/resid_RMS) +
fact3 * quality
where
fact1 is from the reduced IMAGRPRM(11)
fact2 = IMAGPRM(12)
fact3 = IMAGRPRM(13)
maxTaper is the highest beam taper (lowest res)
Taper is the beam taper of the given resolution
resid_peak is the peak residual in the facet
resid_RMS is the robust RMS of the residual
quality is the measure used to pick amoung the
facets at a given resolution and is a function
of peak and average residual.
(14)-(20) Not used at present
IM2PARM....NOTE: these are similar in usage to --- BUT NOT THE SAME
--- as in IMAGR
(1) > 0 => automatically find Clean boxes - Bill Cotton
recommends this option highly.
<= 0 => Clean the full inscribed circle.
(2) > 0 => outlier facets are included (from the NVSS
catalog provided with AIPS) up to IM2PARM(2) degrees
from the phase center.
(3) Minimum estimated flux density in Jy of outlier
sources to be included. 0 -> 0.05
(4) Spectral index to be used in estimating flux
densities from the NVSS fluxes. 0 -> -0.7
(5) If > 1, average the data in time in a baseline
dependent fashion where IM2P(11) is the maximum
allowable amplitude loss due to the averaging.
Values between 1.004 and 1.01 give a good tradeoff
between dynamic range and data set size reduction.
(6) Field of view over which IM2P(11) applies with FOV
as the default.
(7)-(10) Not used at present.
(11) Maximum number of Phase self-cal loops 0 -> none
(12) Minimum flux (Jy) before Phase self-cal is done
(13) Solution interval for Phase self-cal (min)
(14) Maximum number of A&P self-cal loops 0 -> none
(15) Minimum flux (Jy) before A&P self-cal is done
(16) Solution interval for A&P self-cal (min)
(17) min S/N ratio for self-cal solutions. 0 -> 5
(18) min number antennas for a SC solution. 0 -> 3
(19) > 0 -> constrain the mean overall gain
(20) > 0 -> omit negative Clean components (after they
are merged). This is a good idea for bad initial
models and a bad idea for later high-dynamic range
and good models.
(21) Maximum number of peeling self calibration loops. 0
-> no peeling
(22) The minimum flux (Jy) to initiate a peeling self-cal
operation.
(23) Reference antenna for peeling, 0 -> REFANT.
(24) Minimum allowed SNR in peeling self-cal solution.
(25) Peel self-cal solution interval in minutes.
(26) Minimum Clean flux density in peeling
(27) Maximum number of components in Peel Clean
(28) > 0 -> do 'A&P' in last Peel loop, 'P' is done in
all earlier Peel loops
(29) > 0 -> do 'L1' solutions in Peel self-cals
(30)-(40) Not used at present.
REFANT.....The desired reference antenna for phase self-cal.
SOLTYPE....Solution type in self-cal.
' ' => normal least squares,
'L1 ' => L1 solution; a weighted sum of the moduli
of the residuals is minimized.
The computed gain solutions are less
influenced by wild data points, but there
is some loss of statistical efficiency.
See [F.R. Schwab, VLA scientific Memo #136]
for further details.
WTUV.......The weighting factor for data outside of the uv range
defined by UVRANGE during self-cal. 0 -> 0.01
NGAUSS.....Number of scales to use in multi-scale imaging beyond the
basic untapered scale. 0 -> no multi-scale
WGAUSS.....Circular imaging taper specified in units of pixels.
Full resolution is usually from 3 to 8 pixels. Do not
include the untapered scale! NOTE: THIS IS COMPLETELY
DIFFERENT FROM THE UNITS IN IMAGR.
MAXPIXEL...The maximum number of pixels that are searched for
components in each major cycle. < 3000 -> 20050.
This number affects the cpu usage significantly. Too
many causes the task to search over many points it will
never use. Too few causes the task to do many more small
major cycles, also at great expense. Use this with great
caution, but big wins are possible using larger sizes on
very large Cleans.
PRTLEV.....Level of messages desired. 0 -> 2 which is the usual
IMAGR level of messages. Use 1 for a modest set of
messages and 3 for more than you would normally want.
DOTV.......> 0 => try to use ObitView to view and interact with the
imaging process. ObitView needs to be running for
this to work probably.
<= 0 => don't try.
NTHREAD....Use this number of threads when executing Imager. 0 ->
1. Imager will make excellent use of multi-threading.
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.
EXPLAIN SECTION
***************************************************************
***************************************************************
Note that most of these capablities are not offered by
the OBITMAP verb. The full Imager help file follows:
***************************************************************
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Imager Imaging task for radio interferometry data
Type: Task
Use: Batch processing of radio interferometry data
The products of this task are a CLEAN image.
Unless otherwise specified, a fly's eye pattern of
fields with circular CLEAN boxes will be used to cover the specified
field of view (FOV). When processing is finished, the CLEAN images
are "flattened" onto a single image.
If multiple sources are being processed, some failures are allowed.
In this case, the error messages will be displayed and the Status in
the PS table set to "Failed " rather than "Done ".
Greisen variant of Steer-Dewdney-Ito CLEAN implemented via
SDIGain
If BLFact > 1.0 then the input data will be subjected to a
baseline dependent time averaging.
Adverbs:
DataType..'FITS' or 'AIPS' type of input
inFile.....FITS input uvdata if Type=='FITS'
inName.....Input multisource UV data file
inClass....Input UV data file (class). Standard defaults.
inSeq......Input UV data file (seq. #). 0 => highest.
inDisk.....Input UV data file disk drive #. 0 => any.
Data selection
doPS.......If true, the PS (Processing Summary) table,
if it exists, is searched and fields already processed,
present and Status 'Done' will not be reprocessed.
Sources....List of sources (pointings) to be processed.
'*' or blank = all; a "-" before a source name
means all except ANY source named.
Qual.......Only sources with a source qualifier number in the
SU table matching Qual will be used if Qual is not
-1. Qual affects the selection of both the list of
sources and the list of calibrators.
souCode....Calibrators may be selected on the basis of the
calibrator code given in the SU table.
' ' => any calibrator code selected
'* ' => any non blank code (cal. only)
'-CAL' => blank codes only (no calibrators)
anything else = calibrator code to select.
NB: The souCode test is applied in addition to the
other tests, i.e. Sources and Qual, in the
selection of sources to process.
timeRange..Time range of the data to be processed. In order:
Start and end times in days relative to ref. date.
Use dhms2day to convert from human readable form
Stokes.....Stokes parameters to process.
'I' = Stokes I only, 'IQU' = also Q, U
'RR', 'LL' also.
' ' => I, Q, U,
'F'=> formal I (both orthogonal Stokes needed)
FreqID.....Frequency identifier to select , <=0=>any
BChan......First channel number to image, 0=>1. Channel numbers are 1
relative as defined in the input data file.
EChan......Highest channel number to to include in image,
0 => max
RChan......Channel number to restart CLEAN
0 => BChan
chInc......Increment between channels to image in spectral cube.
This is after averaging due to BLchAvg
chAvg......Number of channels to average, 0=> all
This is after averaging due to BLchAvg
BIF........First IF to process. 0=>1
EIF........Highest IF to process 0=> do BIF to highest.
Note: not all data sets will have IFs.
subA.......Sub-array number to use. 0=>all.
doCalib....If true, apply SN or CL table
gainUse....CL/SN table version number to apply. 0=> highest.
doBand.....If true (>0) then correct the data for the shape of the
antenna bandpasses using the BP table specified by BPVer.
The correction has five modes:
(a) if doBand=1 all entries for an antenna in the table
are averaged together before correcting the data.
(b) if doBand=2 the entry nearest in time (including
solution weights) is used to correct the data.
(c) if doBand=3 the table entries are interpolated in
time (using solution weights) and the data are then
corrected.
(d) if doBand=4 the entry nearest in time (ignoring
solution weights) is used to correct the data.
(e) if doBand=5 the table entries are interpolated in
time (ignoring solution weights) and the data are then
corrected.
Imager uses doBand as the nearest integer; 0.1 is therefore
no correction.
BPVer......Specifies the version of the AIPS BP table to be applied
0 => highest numbered table.
<0 => no bandpass correction to be applied.
flagVer....AIPS FG table to use for editing. 0 => highest.
doPol......>=1 apply polarization calibration
Alpha......If != 0.0 then correct data by spectral index Alpha before
imaging and self calibration.
-0.7 is typical for synchrotron.
BLFact.....Baseline dependent time averaging factor.
If BLFact>1.00 then the input data is time averaged in
a baseline dependent fashion and written to the output
data for further processing.
Use the following parameters:
BLFact = Maximum allowable amplitude loss due to time
averaging
BLFOV = Field of view over which the amplitude distortion
is not to exceed BLFact.
The lesser of solPInt and solAInt is used for the
maximum averaging time.
If both are zero, 1 min. is used
This option can substantially reduce the data volume and
reduce processing time.
A value between 1.004 and 1.01 give a good tradeoff between
dynamic range and data reduction.
BLFOV......The radius of the field of view over which baseline
dependent averaging is not to distort amplitudes by more
than BLFact. Defaults to FOV.
BLchAvg....If doing baseline dependent averaging then also average
selected channels by no more than will give bandwidth
smearing of BLFact.
doFull.....If True make full field (flattened) image
Output files
outDType..'FITS' or 'AIPS' type of output
Defaults to DataType.
outFile....Ending of output FITS image file name
filename = source_name+Stokes+outFile
outName....Ending of output AIPS Image Name,
Name = source_name+Stokes+outName
outClass...Output image class. Default = 'ICLEAN'
Only the last 5 characters given are used and the
first is replaced with the Stokes.
Output image name = pointing name (SOURCES)
The output CLEAN image will be used during
execution as the residual image.
outSeq.....Output image sequence number.
outDisk....The disk drive # of output images. 0 => highest
with space (note: map and Beam go on same disk.
CCVer......CC table version number for continuum data only.
For line data the channel number is used for the
version number.
out2File...Ending of output FITS UV data file name
filename = source_name+Stokes+out2File
Defaults to 'UV'
This file will contain the last selected data
with any calibration tables.
out2Name...Ending of output AIPS UV data Name,
Name = source_name+Stokes+out2Name
Defaults to 'UV'
This file will contain the last selected data
with any calibration tables.
out2Class..Output uv data class. Default = 'IMAGER'
out2Seq....Output AIPS uv data sequence number.
out2Disk...The disk drive # of output uv date. 0 => highest
with space. default = outDisk
The following control imaging:
FOV........Radius of the desired field of view in deg..
NField.....Optional parameter to specify fields and overrides
the FOV parameter. Up to 64 may be specified as
parameters; you should have a good reason for doing
this as the default behavior is usually what is
desired.
xCells [optional] Image cell spacing in X in asec.
If left 0 then the program will compute the value
from the data. All fields use the same value.
yCells [optional] Image cell spacing in Y in asec.
If left 0 then the program will compute the value
from the data. All fields use the same value.
nx.........[optional] Number of x pixels in each field specified.
ny.........[optional] Number of y pixels in each field specified.
RAShift....[optional] RA shift (asec) per field
DecShift...[optional] Dec shift (asec) per field
Catalog....Name of FITS file containing outlier catalog
Default NVSSVZ.FIT
This must be in the form of an "AIPS VZ" table.
'None' =. Use no outliers
OutlierDist..max. distance from pointing to include (deg)
default = 10
OutlierFlux..min. estimated flux density (Jy)
default = 0.05
OutlierSI....Spectral index to use, default = -0.7
OutlierSize.. Size in pixels of confusing fields, default 50
NB: This should not be so large as to cause the
outlying fields to be larger than the fields tiling
the FOV or the program may die.
UVTaper....(U,V) Gaussian taper (kilo-lambda) at 30 percent level
as (major, minor axis, position angle)
UVRange....(Minimum,Maximum) baseline (kilo-lambda) to
process.
Robust.....Briggs' "robustness" parameter. "Uniform" weights are
tempered by a constant being added to the local density of
weights. Robust = -4 is nearly pure uniform weighting,
Robust = +4 is nearly pure natural weighting. Use of this
option requires a second array in the memory and may
therefore force the data to be sorted. The option is
turned off if Robust < -7 and uniform weighting is turned
off is Robust > 7.
WtBox......(U,V) box size for weighting. This is the support radius
over which a sample is counted. I.e., the sample or its
weight is counted over an area 2*WtBox+1 cells on each side
in the UV plane, where the UV cell size is (after
correcting units) given by 1 / (UVSIZE(i) * Cellsize).
WtFunc.....If WtBox > 0, WtFunc controls how the samples are counted
as a function of u and v (WtFunc < 0) or of radius (WtFunc
> 0). In the latter case, the function is 0 for radius >
WtBox. Functions are pill box, linear, exponential, and
Gaussian for abs(WtFunc) = 1-4, resp. 0 -> 1.
doFull.....Make full field (flattened) image?
Otherwise only make facets and leave them.
doRestore..Restore CCs to images?
do3D.......If True, make the reference pixel in each facet tangent
to the celestial sphere, else on single tangent plane.
If False, CLEAN components are left on flattened image.
The following control CLEANing:
CLEANBox...A 4x50 array with the specification of a search
area.
Box(1,i)=-1 indicates a circle of radius Box(2,i)
pixels centered on (Box(3,i), Box(4,i))
Box(1,i) >= 0 indicates a rectangular box.
0 => full and inner fields.
If a round box is specified with pixel positions<=0 then
the box will be centered on the center of the image.
Note: the default boxes are set on the basis of
the image size, tilling pattern and autoWindow
autoWindow.If true, automatically set boxes around significant
emission. (Highly recommended)
Gain.......The CLEAN loop gain. 0 => 0.10.
minFlux...Stop Clean when abs(resid. image max) < minFlux (Jy)
If minFlux < 0 then Clean stops at first negative Clean
Component.
minPatch..Minimum half width of the portion of the beam
which is used in the minor CLEAN. Default 500
Niter.....CLEAN iteration limit. 0 => 1500
ccfLim....Limit CLEAN in each major cycle not to CLEAN below
ccfLim times the initial residual peak.
If using SDIGain, set to the maximum value of 0.9.
SDIGain...Fraction of pixels in the upper half of the pixel
histogram to trigger SDI mode. <=0 -> no SDI CLEAN.
If this test is satisfied then all pixels above
a threshold determined will be the site of a new CLEAN
component with a value depending on the local density
of pixels above this threshold.
This is the Greisen implementation of Steer-Dewdney-Ito
CLEAN.
A value of 0.1 is a reasonable initial value
Beam......CLEAN restoring beam major, minor axis size in asec and
the position angle. If zeroes, fit beam.
Reuse.....If >0 then each cycle of self cal after the first will
begin with all summed components whose abs value exceeds
Reuse*RMS(Field 1). Default 10
autoCen...If the sum of the clean components within 1.5 pixels
of any pixel exceeds autoCen and is not within 0.05 of a cell
of a pixel then the image is remade and deconcolved with the
bright sources (>autoCen, one per facet) on a pixel.
This is necessary to achieve high dynamic range.
If the initial dirty image has a pixel brighter than autoCen
then it presumes that the final image will need centering and
the initial CLEAN is stopped at minFlux=0.1*autoCen
Cmethod...This determines the method used to compute the
model visibility values.
'DFT' uses the direct Fourier transform, this
method is the most accurate.
'GRID' does a gridded-FFT interpolation model
computation.
' ' allows the program to use the fastest
method.
PBCor......Apply Frequency dependent primary beam corrections?
antSize....Diameter of antenna for PBCor (m), default = 25
CCFilter...Clean component filtering parameters.
If [0] > 0.0 then for each CLEAN conponent, the
sum of all components within CCFilter[1] cells
is determined, and if less than CCFilter[0], the
component is rejected.
This is done after all self-calibration, CLEANing is done
and if necessary the residuals remade.
maxPixel...The maximum number of pixels that are searched for
components in each major cycle. < 3000
=> 20050. This number affects the cpu usage significantly.
Too many causes the task to search over many points it will
never use. Too few causes the task to do many more small
major cycles, also at great expense. Use this with great
caution, but big wins are possible using larger sizes on
very large Cleans.
Selfcal info
Either phase only or amplitude and phase or both types of
Self calibration can be performed. If both are done, then
phase calibration is done first and applied to the data before
Amp & Phase self calibration. In any case, there will be an
SN table attached to the output uv data which is needed to
fully calibrate it.
maxPSCLoop..Maximum number of phase self calibration loops
minFluxPSC..Min. peak flux density required for phase self cal (Jy)
solPInt.....phase SC Solution interval (min)
solPType....phase SC Solution Type: ' ', 'L1',
solPMode....phase SC Solution Mode:'A&P', 'P', 'P!A',
maxASCLoop..Maximum number of A&P self calibration loops
minFluxASC..Min. peak flux density required for A&P self cal (Jy)
solAInt.....A&P SC Solution interval (min)
solAType....A&P SC Solution Type: ' ', 'L1',
solAMode....A&P SC Solution Mode:'A&P', 'P', 'P!A',
refAnt......Reference antenna number for selfcal
WtUV........Weighting (wrt 1) to use outside of basic uv range in SC
avgPol......Average Polarizations in self calibration?
avgIF.......Average IFs in self calibration?
noNeg.......If True, exclude negative summed CLEAN components from the
self-cal model calculation. This is useful if the initial
calibration is poor and there are negative components due
to phase errors but is harmful if the initial calibration is
relatively good and the negative components are needed to
describe a high dynamic range image (say DR>1000:1)
doMGM.......Apply mean gain modulus to A&P selfcal soln.
minSNR......Min. allowed SNR in self cal solution
minNo.......Min. allowed no. antennas in selfcal
prtLv.......Print level in selfcal, 0=>none
Peeling
PeelFlux....Peeling is the procedure of doing a self calibration on
a single source, removing it and reverting to the
previous calibration. This is useful for a very strong
source whose artifacts disturb the other parts of the
field. If the maximum pixel value in any image
(as defined by the CLEAN components) exceeds PeelFlux,
then the facet in which the maximum value occured is
peeled. This procedure is iterated until no facet has a
pixel in excess of PeelFlux.
NB: peeling of many sources will likely degrade the
results.
It is strongly recommended that autoCen be no larger
than PeelFlux so that the source is properly centered in
its facet.
PeelLoop....Maximum number of peeling self calibration loops
PeelRefAnt..Reference antenna number for Peel selfcal
PeelSNRMin..Min. allowed SNR in peeling self cal solution
PeelSolInt..Peel SC Solution interval (min)
PeelType....Peel SC Solution type ' ', 'L1'
PeelMode....Peel SC Solution mode:'A&P', 'P', 'P!A',
"P" is used for all but the last peel which uses PeelMode
PeelNiter...Max. number of components in Peel CLEAN
PeelMinFlux.Min. Peel CLEAN flux density
PeelAvgPol..Average Polarizations in Peel self calibration?
PeelAvgIF ..Average IFs in Peel self calibration?
Multiresolution CLEAN
A multiresolution CLEAN is enabled using nTaper>0.
This allows multiple circular imaging tapers to be
specified in units of pixels; full resolution is
generally 3-8 pixels. The full mosaic is reproduced in
each resolution
Each major cycle, which resolution is to be used is
picked on the basis of image statistics, the weightings
of which are controled by MResKnob.
The objective function used to chose the resolution is
given by:
fact1 * (maxTaper - Taper)/maxTaper +
fact2 * (resid_peak/resid_RMS) +
fact3 * quality
where
fact1 is from the reduced MResKnob[0]
fact2 = MResKnob[1]
fact3 = MResKnob[2]
maxTaper is the highest beam taper (lowest res)
Taper is the beam taper of the given resolution
resid_peak is the peak residual in the facet
resid_RMS is the robust RMS of the residual
quality is the measure used to pick amoung the facets
at a given resolution and is a function of peak and
average residual.
The comparison is performed on the facet at each
resolution with the highest "quality".
nTaper......Number of resolutions expressed as the number of tapers
to be applied to the data
Tapers......List of circular Gaussian tapers in (x) pixels.
MResKnob....Controls on selecting resolution to be CLEAned next.
[0] Bias towards higher resolution, 0=>0.2
As the CLEAN progresses, this factor is reduced by
(1-iteration/niter)**3
[1] SNR factor, 0=>0.35
[2] "Quality" factor, 0=>0.2
Interactive display
dispURL.....The URL of the display server to use. "None"=>none
"ObitView" = "http://localhost:8765/RPC2"
This will display fields being CLEANed and allow
interactive editing of the CLEAN window.
If the display is running on a machine on which the
data is not visible, use "http://myhost:port/RPC2"
where myhost is the network name and port is the port
number (usually 8765), Example:
dispURL="http://canis.cv.nrao.edu:8765/RPC2"
nThreads....If The Obit libraries are compiled with multiple
thread operation enabled, this parameter sets the
number of threads that can be used for parallel
operations.
NB: This only improves performance if there are
multiple processors and/or cores in the host.
taskLog.....Log file to write messages to INSTEAD of the terminal
This is useful in long runs or batch files where
a bug in the ObitTalk message handling may cause
tasks to hang. Path is absolute or relative to where
the task executes.
noScrat.....A list of AIPS disk numbers on which you do not
wish scratch files