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== Help on clean task: ==
Invert and deconvolve images with selected algorithm
      The clean task has many options:
        1)  Make 'dirty' image and 'dirty' beam (psf)
        2)  Multi-frequency-continuum images or spectral channel imaging
        3)  Full Stokes imaging
        4)  Mosaicking of several pointings
        5)  Multi-scale cleaning
        6)  Widefield cleaning
        7)  Interactive clean boxing
        8)  Use starting model (eg from single dish)
      vis -- Name of input visibility file
              default: none; example: vis='ngc5921.ms'
      imagename -- Pre-name of output images:
              default: none; example: imagename='m2'
              output images are:
                m2.image; cleaned and restored image
                        With or without primary beam correction
                m2.psf; point-spread function (dirty beam)
                m2.flux;  relative sky sensitivity over field
                m2.flux.pbcoverage;  relative pb coverage over field
                                      (gets created only for ft='mosaic')
                m2.model; image of clean components
                m2.residual; image of residuals
                m2.interactive.mask; image containing clean regions
              To include outlier fields:
      outlierfile --- Text file name which contains image names, sizes, field
      field -- Select fields to image or mosaic.  Use field id(s) or name(s).
                  ['go listobs' to obtain the list id's or names]
              default: ''= all fields
                If field string is a non-negative integer, it is assumed to
                be a field index otherwise, it is assumed to be a
                field name
                field='0~2'; field ids 0,1,2
                field='0,4,5~7'; field ids 0,4,5,6,7
                field='3C286,3C295'; field named 3C286 and 3C295
                field = '3,4C*'; field id 3, all names starting with 4C
      spw -- Select spectral window/channels
              NOTE: channels de-selected here will contain all zeros if
              selected by the parameter mode subparameters.   
              Channel selection behaves differently in clean (e.g. The multiple
              ranges are not supported yet).
              default: ''=all spectral windows and channels
                spw='0~2,4'; spectral windows 0,1,2,4 (all channels)
                spw='0:5~61'; spw 0, channels 5 to 61
                spw='<2';  spectral windows less than 2 (i.e. 0,1)
                spw='0,10,3:3~45'; spw 0,10 all channels, spw 3,
                                    channels 3 to 45.
                spw='0~2:2~6'; spw 0,1,2 with channels 2 through 6 in each.
      selectdata -- Other data selection parameters
              default: True
  >>> selectdata=True expandable parameters
              See help par.selectdata for more on these
              timerange  -- Select data based on time range:
                  default: '' (all); examples,
                  timerange = 'YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss'
                  Note: if YYYY/MM/DD is missing date defaults to first
                        day in data set
                  timerange='09:14:0~09:54:0' picks 40 min on first day
                  timerange='25:00:00~27:30:00' picks 1 hr to 3 hr
                            30min on NEXT day
                  timerange='09:44:00' pick data within one integration
                            of time
                  timerange='>10:24:00' data after this time
              uvrange -- Select data within uvrange (default units meters)
                  default: '' (all); example:
                  uvrange='0~1000klambda'; uvrange from 0-1000 kilo-lambda
                  uvrange='>4klambda';uvranges greater than 4 kilo lambda
              antenna -- Select data based on antenna/baseline
                  default: '' (all)
                  If antenna string is a non-negative integer, it is
                  assumed to be an antenna index, otherwise, it is
                  considered an antenna name.
                  antenna='5&6'; baseline between antenna index 5 and
                                index 6.
                  antenna='VA05&VA06'; baseline between VLA antenna 5
                                      and 6.
                  antenna='5&6;7&8'; baselines 5-6 and 7-8
                  antenna='5'; all baselines with antenna index 5
                  antenna='05'; all baselines with antenna number 05
                                (VLA old name)
                  antenna='5,6,9'; all baselines with antennas 5,6,9
                                  index numbers
              scan -- Scan number range.
                  default: '' (all)
                  example: scan='1~5'
                  Check 'go listobs' to insure the scan numbers are in order.
      mode -- Frequency Specification:
              NOTE: Channels deselected with spw parameter will contain all
              See examples below.
              default: 'mfs'
                mode = 'mfs' means produce one image from all
                      specified data.
                mode = 'channel'; Use with nchan, start, width to specify
                        output image cube.
                mode = 'velocity', channels are specified in velocity.
                mode = 'frequency', channels are specified in frequency.
  >>> mode='mfs' expandable parameters
              Make a continuum image from the selected frequency
              channels/range using Multi-frequency synthesis
              algorithm for wide-band narrow field imaging.  nterms
              is the number of Taylor terms to be used to model the
              frequency dependence of the sky emission.  nterms=1 is
              equivalent to assuming no frequency dependence.
              nterms=2 is equivalent to the Sault-Wieringa algorithm
              (AandAS, 1994) reffreq is the reference frequency about
              which the Taylor expansion is done. ** Note that the
              software implementation of the algorithm for nterms>1
              is still experimental and will be fully available in a
              later release. **
  >>> mode='channel', 'velocity', and 'frequency' expandable parameters
              nchan -- Total number of channels in the output image.
                Example: nchan=100.
                Default: -1; Automatically selects enough channels to cover
                data selected by 'spw' and consistent with 'start' and 'width'.
                It is often easiest to leave nchan at the default value.
              start -- First channel, velocity, or frequency.
                For mode='channel'; This selects the channel index number
                from the MS (0 based) that you want to correspond to the first
                channel of the output cube. The output cube will be in frequency
                space with the first channel having the frequency of the
                MS channel selected by start.  start=0 refers to the first
                channel in the first selected spw, even if that channel
                is de-selected in the spw parameter. Channels de-selected by
                the spw parameter will be filled with zeros if included by
                the start parameter. For example, spw=3~8:3~100 and start=2
                will produce a cube that starts on the third channel (recall 0
                based) of spw index 3, and the first channel will be blank.
                For mode='velocity' or 'frequency': default='';
                starts at first input channel of first input spw
                examples: start='5.0km/s', or start='22.3GHz'.
              width -- Output channel width
                For mode='channel', default=1; >1 indicates channel averaging
                example: width=4.
                For mode=' 'velocity' or 'frequency', default=''; width of
                first input channel, or more precisely, the difference
                in frequencies between the first two selected channels.
                (for example if channels 1 and 3 are selected with spw,
                  then the default width will be the difference between their
                  frequencies, and not the width of channel 1)
                When not using the default, one must give units
                examples: width='1.0km/s', or width='24.2kHz'.
                Setting width>0 gives channels of increasing frequency for
                mode='frequency', and increasing velocity for mode='velocity'.
              interpolation -- Interpolation type for spectral gridding onto
                the uv-plane. Options: 'nearest', 'linear', or 'cubic'.
                default = 'linear'
              chaniter -- specify how spectral CLEAN is performed,
                default: chaniter=False;
                example: chaniter=True; step through channels
                  WARNING: The interactive clean with chaniter=True for
                    optical velocity mode
                    (mode='velocity' and veltype='optical') is
                    NOT YET IMPLEMENTED.
              outframe -- For mode='velocity', 'frequency', or 'channel':  velocity
                reference frame of output image
                Options: '','LSRK','LSRD','BARY','GEO','TOPO','GALACTO',
                default: ''; same as input data
                example: frame='bary' for Barycentric frame
              veltype -- for mode='velocity' gives the velocity definition
                Options: 'radio','optical'
                default: 'radio'
                NOTE: the viewer always defaults to displaying the 'radio'
                  frame, but that can be changed in the position tracking
                  pull down.
          mode='mfs' examples:
              spw = '0,1'; mode = 'mfs'
                  will produce one image made from all channels in spw
                      0 and 1
              spw='0:5~28^2'; mode = 'mfs'
                  will produce one image made with channels
          mode='channel' examples:
              spw = '0'; mode = 'channel': nchan=3; start=5; width=4
                  will produce an image with 3 output planes
                  plane 1 contains data from channels (5+6+7+8)
                  plane 2 contains data from channels (9+10+11+12)
                  plane 3 contains data from channels (13+14+15+16)
              spw = '0:0~63^3'; mode='channel'; nchan=21; start = 0;
                  width = 1
                  will produce an image with 20 output planes
                  Plane 1 contains data from channel 0
                  Plane 2 contains date from channel 2
                  Plane 21 contains data from channel 61
              spw = '0:0~40^2'; mode = 'channel'; nchan = 3; start =
                  5; width = 4
                  will produce an image with three output planes
                  plane 1 contains channels (5,7)
                  plane 2 contains channels (13,15)
                  plane 3 contains channels (21,23)
      psfmode -- method of PSF calculation to use during minor cycles:
              default: 'clark': Options: 'clark','clarkstokes', 'hogbom'
              'clark'  use smaller beam (faster, usually good enough);
                for stokes images clean components peaks are searched
              in the I^2+Q^2+U^2+V^2 domain
              'clarkstokes' locate clean components independently in
              each stokes image
              'hogbom' full-width of image (slower, better for poor
              Note:  psfmode will also be used to clean if imagermode = ''
      imagermode -- Advanced imaging e.g. mosaic or Cotton-Schwab clean
              default: imagermode='': Options: '', 'csclean', 'mosaic'
              default ''  => psfmode cleaning algorithm used
  >>> gridmode='' expandable parameters
              The default value of '' has no effect.
  >>> gridmode='widefield' expandable parameters
              Apply corrections for non-coplanar effects during imaging
              using the W-Projection algorithm (Cornwell et al. IEEE JSTSP
              (2008)) or faceting or a combination of the two.
              wprojplanes is the number of pre-computed w-planes used for
                  the W-Projection algorithm.  wprojplanes=1 disables
                  correction for non-coplanar effects.
              facets is the number of facets used.  W-Projection is done
                  for each facet.
  >>> gridmode='aprojection' expandable parameters
              Corrects for the (E)VLA polarization squint using the
              A-Projection algorithm (Bhatnagar et al., AandA (2008)).
              cfcache is the name of the directory to be used to cache the
                  convolution functions.  These functions can be reused
                  again if the image parameters are unchanged.  If the image
                  parameters change, a new cache must be created (or the
                  existing one removed).
              painc (in degrees) is the Parallactic Angle increment used to
                  compute the convolution functions.
  >>> imagermode='mosaic' expandable parameter(s):
              Make a mosaic of the different pointings (uses csclean style
              mosweight -- Individually weight the fields of the mosaic
                  default: False; example: mosweight=True
                  This can be useful if some of your fields are more
                  sensitive than others (i.e. due to time spent
                  on-source); this parameter will give more weight to
                  higher sensitivity fields in the overlap regions.
              ftmachine -- Gridding method for the mosaic;
                  Options: 'ft' (standard interferometric gridding), 'sd'
                  (standard single dish),
                  and 'mosaic' (grid using PB as convolution function).
                  default: 'mosaic';
                  ONLY if imagermode='mosaic' is chosen and
                  ftmachine='mosaic', is heterogeneous imaging (CARMA, ALMA)
                  possible using the right convolution of primary beams for
                  each baseline.
              scaletype -- Controls scaling of pixels in the image plane.
                  (Not fully implemented...for now only controls
                  what is seen if interactive=True...but in the future will
                  control the image on which clean components are searched)
                  default='SAULT'; example: scaletype='PBCOR'
                  Options: 'PBCOR','SAULT'
                    'SAULT' when interactive=True shows the residual
                            with constant noise across the mosaic.
                            be acheived by setting pbcor=True.
                    'PBCOR' uses the SAULT scaling scheme for
                            deconvolution, but if interactive=True shows the
                            primary beam corrected image during interactive.
  >>> imagermode='csclean' expandable parameter(s):
              Image using the Cotton-Schwab algorithm in between major cycles
              cyclefactor -- Change the threshold at which the deconvolution
                  cycle will stop, degrid and subtract from the visibilities 
                  For poor PSFs, reconcile often (cyclefactor=4 or 5);
                  For good PSFs, use cyclefactor 1.5 to 2.0.
                  Note: threshold = cyclefactor * max sidelobe * max residual
                  default: 1.5; example: cyclefactor=4
              cyclespeedup -- Cycle threshold doubles in this number of
                  default: -1;
                  example: cyclespeedup=3
                  try cyclespeedup = 50 to speed up cleaning
      multiscale -- set of scales to use in deconvolution.  If set,
              cleans with several resolutions using hobgom clean. The
              scale sizes are in units of cellsize.  So if
              cell='2arcsec', a multiscale scale=10 = 20arcsec.  First
              scale should always be 0 (point), we suggest second on
              the order of synthesized beam, third 3-5 times
              synthesized beam, etc. For example if synthesized beam
              is 10" and cell=2", try multscale = [0,5,15]. Note,
              multiscale is currently a bit slow.
              default: multiscale=[] (standard CLEAN with psfmode algorithm,
              no multi-scale). Example:  multiscale = [0,5,15]
  >>> multiscale expandable parameter(s):
              negcomponent -- Stop component search when the largest scale
                has found this number of negative components;
                -1 means continue component search even if the largest
                component is negative.  default: -1; example: negcomponent=50
              smallscalebias -- A bias toward smaller scales.
                  The peak flux found at each scale is weighted by
                  a factor = 1 - smallscalebias*scale/max_scale, so
                  that Fw = F*factor.
                  Typically the values range from 0.2 to 1.0.
                  default: 0.6
      imsize -- Image pixel size (x,y).  DOES NOT HAVE TO BE A POWER OF 2
              default = [256,256]; example: imsize=[350,350]
              imsize = 500 is equivalent to [500,500]
              If include outlier fields, e.g., [[400,400],[100,100]] or
              use outlierfile.
              Avoid odd-numbered imsize.
      cell -- Cell size (x,y)
              default= '1.0arcsec';
              example: cell=['0.5arcsec,'0.5arcsec'] or
              cell=['1arcmin', '1arcmin']
              cell = '1arcsec' is equivalent to ['1arcsec','1arcsec']
              NOTE:cell = 2.0 => ['2arcsec', '2arcsec']
      phasecenter -- direction measure  or fieldid for the mosaic center
              default: '' => first field selected ; example: phasecenter=6
              or phasecenter='J2000 19h30m00 -40d00m00'
              If include outlier fields,
                e.g. ['J2000 19h30m00 -40d00m00',J2000 19h25m00 -38d40m00']
              or use outlierfile.
      restfreq -- Specify rest frequency to use for output image
              default='' Occasionally it is necessary to set this (for
              example some VLA spectral line data).  For example for
              NH_3 (1,1) put restfreq='23.694496GHz'
      stokes -- Stokes parameters to image
              default='I'; example: stokes='IQUV';
              Options: 'I','IV''QU','IQUV','RR','LL','XX','YY','RRLL','XXYY'
      niter -- Maximum number iterations,
              if niter=0, then no CLEANing is done ("invert" only)
              default: 500; example: niter=5000
      gain -- Loop gain for CLEANing
              default: 0.1; example: gain=0.5
      threshold -- Flux level at which to stop CLEANing
              default: '0.0mJy';
              example: threshold='2.3mJy'  (always include units)
                        threshold = '0.0023Jy'
                        threshold = '0.0023Jy/beam' (okay also)
      interactive -- use interactive clean (with GUI viewer)
              default: interactive=False
              example: interactive=True
              interactive clean allows the user to build the cleaning
              mask interactively using the viewer.  The viewer will
              appear every npercycle interation, but modify as needed
              The final interactive mask is saved in the file
              imagename_interactive.mask.  The initial masks use the
              union of mask and cleanbox (see below).
  >>> interactive=True expandable parameters
              npercycle -- this is the  number of iterations between each
                interactive update of the mask.  It is important to modify
                this number interactively during the cleaning, starting with
                a low number like 20, but then increasing as more extended
                emission is encountered.
      mask -- Specification of cleanbox(es), mask image(s), and/or
              region(s) to be used for CLEANing. As long as the image has
              the same shape (size), mask images from a previous
              interactive session can be used for a new execution. NOTE:
              the initial clean mask actually used is the union of what
              is specified in mask and <imagename>.mask default: [] (no
              masking); Possible specification types: (a) Explicit
              cleanbox pixel ranges example: mask=[110,110,150,145] clean
              region with blc=110,100; trc=150,145 (pixel values) (b)
              Filename with cleanbox pixel values with ascii format:
              example: mask='mycleanbox.txt' <fieldid blc-x blc-y
              trc-x trc-y> on each line
              1 45 66 123 124
              2 23 100 300 340
              (c) Filename for image mask example: mask='myimage.mask'
              (d) Filename for region specification (e.g. from viewer)
              example: mask='myregion.rgn' (e) Combinations of any of the
              above example: mask=[[110,110,150,145],'mycleanbox.txt',
              If include outlier fields, then mask need to be specified in
              nested lists:
                e.g. mask=[[[110,110,150,145],'myimage.mask'],[],[20,20,40,40]]
              (A clean box with [110,110,150,145] and a image mask for main
                field, no mask for 1st outlier field, 1 clean box for second
                outlier field.)
      uvtaper -- Apply additional uv tapering of the visibilities.
              default: uvtaper=False; example: uvtaper=True
  >>> uvtaper=True expandable parameters
              outertaper -- uv-taper on outer baselines in uv-plane
                  [bmaj, bmin, bpa] taper Gaussian scale in uv or
                  angular units. NOTE: the on-sky FWHM in arcsec is roughly
                  the uv taper/200 (klambda).
                  default: outertaper=[]; no outer taper applied
                  example: outertaper=['5klambda']  circular taper
                                FWHM=5 kilo-lambda
                            outertaper=['10arcsec'] on-sky FWHM 10 arcseconds
                            outertaper=['300.0'] default units are meters
                                in aperture plane
              innertaper -- uv-taper in center of uv-plane
                  [bmaj,bmin,bpa] Gaussian scale at which taper falls to
                  zero at uv=0
                  default: innertaper=[]; no inner taper applied
                  NOT YET IMPLEMENTED               
      modelimage -- Name of model image(s) to initialize cleaning. If
              multiple images, then these will be added together to
              form initial staring model NOTE: these are in addition
              to any initial model in the <imagename>.model image file
              default: '' (none); example: modelimage='orion.model'
              modelimage=['orion.model','sdorion.image'] Note: if the
              units in the image are Jy/beam as in a single-dish
              image, then it will be converted to Jy/pixel as in a
              model image, using the restoring beam in the image
      weighting -- Weighting to apply to visibilities:
              default='natural'; example: weighting='uniform';
              Options: 'natural','uniform','briggs',
  >>> Weighting expandable parameters
              For weighting='briggs' and 'briggsabs'
                  robust -- Brigg's robustness parameter
                  default=0.0; example: robust=0.5;
                  Options: -2.0 to 2.0; -2 (uniform)/+2 (natural)
              For weighting='briggsabs'
                  noise  -- noise parameter to use for Briggs "abs"
                  example noise='1.0mJy'
              npixels -- uv-cell area used for weight calculation
                  example npixels=1
                  Default = 0
                  superuniform:  0 Means 3x3 cells for weighting
                    the cell weight is proportional to the weight of
                    the 3x3 cells centered on it.
                  superuniform = F means 1x1 cell for averaging weights.
                  briggs/briggsabs: 0 is similar to 1x1 cell weight.
                    1 may? be similar to 3X3 cells.
                  Only npixels 0 or 1 recommended
      restoringbeam -- Output Gaussian restoring beam for CLEAN image
              [bmaj, bmin, bpa] elliptical Gaussian restoring beam
              default units are in arc-seconds for bmaj,bmin, degrees
              for bpa default: restoringbeam=[]; Use PSF calculated
              from dirty beam.
              example: restoringbeam=['10arcsec'] circular Gaussian
                        FWHM 10 arcseconds example:
                        restoringbeam=['10.0','5.0','45.0deg'] 10"x5"
                        at 45 degrees
      pbcor -- Output primary beam-corrected image
                If pbcor=False, the final output image is NOT corrected for the
                PB pattern (particularly important for mosaics), and therefore is
                not "flux correct". Correction can also be done after the
                fact using immath to divide <imagename>.image by
                the <imagename>.flux image.
              default: pbcor=False; output un-corrected image
              example: pbcor=True; output pb-corrected image (masked outside
      minpb -- Minimum PB level to use default=0.2;
              The flux image is used to determine this
              except for the case of mosaic with ftmachine='mosaic'
              where the flux.pbcoverage image is used.
              example: minpb=0.01 Note: this minpb is always in effect
                        (regardless of pbcor=True/False)
      calready -- if True will create scratch columns if they are
              not there. And after clean completes the predicted model
              visibility is from the clean components are written to the ms.
      async -- Run asynchronously
              default = False; do not run asychronously
                            HINTS ON CLEAN WITH FLANKING FIELDS
              1. Decide if the images will be specified directly in the
                inputs or with an outlier file.  For more than a few fields,
                an outlier file more convenient.
                Direct Method:
                  cell = ['1.0arcsec', '1.0arcsec']
                  imagename = ['M1_0','M1_1','M1_2]
                  imsize = [[1024,1024],[128,128],[128,128]]
                  phasecenter = ['J2000 13h27m20.98 43d26m28.0',
                            'J2000 13h30m52.159 43d23m08.02', 'J2000 13h24m08.16 43d09m48.0']
                Text file method  (in outlier.txt)
                  imagename = 'M1'
                  outlierfile = 'outlier.txt'
                      [phasecenter, imsize ignored]
                  Contents of outlier.txt
                  C 0  1024 1024  13 27 20.98    43 26 28.0
                  C 1    128  128  13 30 52.158    43 23 08.00
                  C 2    128  128  13 24 08.163    43 09 48.00
                In both cases the following images will be made:
                    M1_0.image, M1_1.image, M1_2.image    cleaned images
                    M1.0.model, M1_1.model, M1_2.model    model images
                    M1.0.residual, M1_1.residual, M1_2.residual    residual images
              2. Masks for flanking fields are specified in same way as
                in the single output field case, but need extra '[ ]' to
                distinguish each field.
                    would apply masks:
                    for the first field (main field),
                      myregion.rg and a box defined by [100,100,150,150] in pixels
                    for the seconf field (first outlier), myimage1.mask
                    for the third field (second outlier), no mask (produce a mask for
                    whole field)
                However, if boxfiles are given, ids in the first column of the files
                are used to match with fields (using order given imagename or
                So, if the content of  a boxfile looks like this,
                        0 45 66 123 124
                        1 23 100 300 340
                        2 20 20 40 40
                then [45 66 123 124] is assigned to first field (imagename[0], or first line
                of outlierfile).

Latest revision as of 19:20, 6 May 2015