[daip] IMAGR with multi facets
Eric Greisen
egreisen at nrao.edu
Fri Jun 6 12:06:53 EDT 2008
Gaelle Dumas wrote:
>
> Dear Dr. Greisen,
>
> I am doing images of VLA data of M51 at 3.6 (B+C), 6 (B+C+D) and 20cm
> (A+B+C+D), using multiple fields.
> There is no error or warning messages during the cleaning process,
> however the final maps for the 3.6 and 6cm data have got very bad
> stripped features (see the joint ps file, corresponding to the 3.6cm
> data, north pointing, combination of all the facets)
>
> I checked carefully the calibration steps, and I didn't find any problem
>
> Here is what I did for the 3.6cm, North pointing, to create the clean map:
>
> I run setfc on the uv file with the inputs:
> AIPS 1: SETFC: Task to make a BOXFILE for input to IMAGR
> AIPS 1: Adverbs Values Comments
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: INNAME 'M51_N_4CM_CD' UV dataset name (name)
> AIPS 1: INCLASS 'IF 1+2' UV dataset
> name (class)
> AIPS 1: INSEQ 1 UV dataset name (seq. #)
> AIPS 1: INDISK 1 Disk drive #
> AIPS 1: SOURCES *all ' ' Source selected
> AIPS 1: BCOUNT 1 First field number to use
> AIPS 1: BOXFILE 'WORK:BOX_XBAND_N'
> AIPS 1: disk file to write to (the
> AIPS 1: input BOXFILE for IMAGR)
> AIPS 1: CELLSIZE 0.4 0.4 (X,Y) size of grid in asec
> AIPS 1: IMSIZE 4096 4096 field size
> AIPS 1: SHIFT 0 0 Position shift (RA,Dec) asec
> AIPS 1: for all fields
> AIPS 1: FLUX 2.500E-05 Minimum component flux =
> AIPS 1: (source * beam)
> AIPS 1: BPARM 0.5 5 (1) Inner region radius (deg)
> AIPS 1: *rest 0 (2) Field overlap (pixels)
> AIPS 1: (3) Factor to scale NVSS
> AIPS 1: fluxes, 0 -> 1
> AIPS 1: (4) Radius NVSS search (deg)
> AIPS 1: (5) Flux limit in NVSS (Jy)
> AIPS 1: (6) IMSIZE for NVSS fields
> AIPS 1: (7) IMSIZE for Sun fields
> AIPS 1: (8) Write Clean boxes for
> AIPS 1: NVSS fields
> AIPS 1: (9) Maximum allowed phase
> AIPS 1: error in imaging
> AIPS 1: (10) Points per beaam
> AIPS 1: PBPARM *all 0 Beam parameters:
> AIPS 1: (1) Cutoff; (2) Use (3)-(7)
> AIPS 1: (3)-(7) Beam shape parms
> AIPS 1: INFILE ' '
> AIPS 1: NVSS input file name
> AIPS 1: ' ' => AIPS provided.
>
> this defined 7 facets
>
> then I run imagr with the following inputs
>
> AIPS 1: IMAGR: Wide field imaging/Clean task
> AIPS 1: Adverbs Values Comments
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: INNAME 'M51_N_4CM_CD' Input UV data (name)
> AIPS 1: INCLASS 'IF 1+2' Input UV data (class)
> AIPS 1: INSEQ 1 Input UV data (seq. #)
> AIPS 1: INDISK 1 Input UV data disk drive #
> AIPS 1: SOURCES *all ' ' Source name
> AIPS 1: QUAL -1 Calibrator qualifier -1=>all
> AIPS 1: CALCODE ' ' Calibrator code ' '=>all
> AIPS 1: TIMERANG *all 0 Time range to use
> AIPS 1: SELBAND -1 Bandwidth to select (kHz)
> AIPS 1: SELFREQ -1 Frequency to select (MHz)
> AIPS 1: FREQID -1 Freq. ID to select.
> AIPS 1: SUBARRAY 0 Sub-array, 0=>all
> AIPS 1: DOCALIB -1 If >0 calibrate data
> AIPS 1: = 2 calibrate weights
> AIPS 1: GAINUSE 0 CL (or SN) table to apply
> AIPS 1: DOPOL -1 If >0.5 correct polarization.
> AIPS 1: BLVER -1 BL table to apply.
> AIPS 1: FLAGVER 0 Flag table version
> AIPS 1: DOBAND -1 If >0.5 apply bandpass cal.
> AIPS 1: Method used depends on value
> AIPS 1: of DOBAND (see HELP file).
> AIPS 1: BPVER -1 Bandpass table version
> AIPS 1: SMOOTH *all 0 Smoothing function. See
> AIPS 1: HELP SMOOTH for details.
> AIPS 1: STOKES ' ' Stokes parameters (see HELP)
> AIPS 1: BCHAN 1 Low freq. channel 0 for cont.
> AIPS 1: ECHAN 0 Highest freq channel
> AIPS 1: CHANNEL 0 Restart channel number
> AIPS 1: NCHAV 1 Number of chan. to average.
> AIPS 1: CHINC 1 Channel incr. between maps.
> AIPS 1: BIF 0 First IF in average.
> AIPS 1: EIF 0 Last IF in average.
> AIPS 1: OUTNAME ' ' Output image name (name)
> AIPS 1: OUTDISK 1 Output image disk drive #
> AIPS 1: OUTSEQ 0 Output seq. no.
> AIPS 1: OUTVER 0 CC ver. no (Continuum only)
> AIPS 1: *** SET OUTVER ON RESTARTS
> AIPS 1: IN2NAME ' ' UV work file name
> AIPS 1: IN2CLASS ' ' UV work file class
> AIPS 1: IN2SEQ 0 UV work file seq
> AIPS 1: *** SET TO KEEP WORK FILE
> AIPS 1: IN2DISK 0 UV work file disk
> AIPS 1: CELLSIZE 0.4 0.4 (X,Y) size of grid in asec
> AIPS 1: IMSIZE 4096 4096 Minimum image size
> AIPS 1: NFIELD 7 Number of fields (max 4096)
> AIPS 1: DO3DIMAG 1 > 0 => use different tangent
> AIPS 1: points for each field
> AIPS 1: FLDSIZE *all 0 Clean size of each field.
> AIPS 1: RASHIFT *all 0 RA shift per field (asec)
> AIPS 1: DECSHIFT *all 0 DEC shift per field (asec)
> AIPS 1: UVTAPER 0 0 (U,V) Gaussian taper
> AIPS 1: units are kilo-lambda
> AIPS 1: UVRANGE 0 0 Min & max baseline (klambda)
> AIPS 1: GUARD 0 0 x,y guard band fractional
> AIPS 1: radius
> AIPS 1: ROTATE 0 Rotate image CCW from N by
> AIPS 1: ROTATE degrees
> AIPS 1: ZEROSP 1 0 0-spacing fluxes and weights
> AIPS 1: 0 0 SEE HELP!!
> AIPS 1: 5
> AIPS 1: UVWTFN ' ' UV dist. weight function
> AIPS 1: UVSIZE 0 0 Array size for doing uniform
> AIPS 1: weights. 0 -> actual field
> AIPS 1: size.
> AIPS 1: ROBUST 0 Robustness power: -5 -> pure
> AIPS 1: uniform weights, 5 => natural
> AIPS 1: UVBOX 0 Additional rows and columns
> AIPS 1: used in weighting.
> AIPS 1: UVBXFN 1 Box function type when UVBOX
> AIPS 1: > 0. 0 -> 1 round pill box.
> AIPS 1: XTYPE 5 Conv. function type in x
> AIPS 1: default spheroidal
> AIPS 1: YTYPE 5 Conv. function type in y
> AIPS 1: default spheroidal
> AIPS 1: XPARM *all 0 Conv. function parms for x
> AIPS 1: YPARM *all 0 Conv. function parms for y
> AIPS 1: NITER 50000 Maximum # of Clean components
> AIPS 1: BCOMP *all 0 Begin at BCOMP component
> AIPS 1: Specify for each field.
> AIPS 1: ALLOKAY 0 For restart: > 0 => beams
> AIPS 1: okay, > 1 => work file too
> AIPS 1: NBOXES 0 Number of boxes for Clean
> AIPS 1: NB: field 1 only.
> AIPS 1: CLBOX *all 0 Four coordinates for each box
> AIPS 1: BOXFILE 'WORK:BOX_XBAND_N' Input file of field params
> AIPS 1: and Clean boxes; ' ' => use
> AIPS 1: FLDSIZE, RASHIFT, DECSHIFT,
> AIPS 1: NBOXES, CLBOX only.
> AIPS 1: OBOXFILE 'WORK:BOX_XBAND_N_CLEAN'Output file for final Clean
> AIPS 1: boxes
> AIPS 1: GAIN 0.1 Clean loop gain
> AIPS 1: FLUX 2.500E-05 Minimum Clean component (Jy)
> AIPS 1: MINPATCH 121 Min. BEAM half-width in AP.
> AIPS 1: BMAJ 0 FWHM(asec) major axis Clean
> AIPS 1: restoring beam.
> AIPS 1: BMIN 0 FWHM(asec) minor axis Clean
> AIPS 1: restoring beam.
> AIPS 1: BPA 0 Clean beam position angle
> AIPS 1: OVERLAP 2 1 => restore components to
> AIPS 1: overlapped fields, >=2=>
> AIPS 1: expect overlaps in Cleaning
> AIPS 1: PHAT 0 Prussian hat height.
> AIPS 1: FACTOR 0 Speedup factor see HELP
> AIPS 1: CMETHOD ' ' Modeling method:
> AIPS 1: 'DFT','GRID',' '
> AIPS 1: IMAGRPRM *all 0 Task enrichment parameters
> AIPS 1: (1) Antenna diameter (m)
> AIPS 1: (2) Source Spectral index
> AIPS 1: (3) Frequency scaling factor
> AIPS 1: (4) > 0 -> SDI Clean factor
> AIPS 1: (5) >0 => scale residuals
> AIPS 1: (6) Half-width in x of box
> AIPS 1: (7) Half-width in y of box
> AIPS 1: (8) Filter components whose
> AIPS 1: neighborhood is weaker than
> AIPS 1: IMAGRPRM(8) Jy. 0 -> don't
> AIPS 1: (9) Radius in pixels for the
> AIPS 1: IMAGRPRM(8) test.
> AIPS 1: (10) multiplier of image size
> AIPS 1: to get beam size: 0 => 2;
> AIPS 1: 2, 1, 0.5 0.25 supported
> AIPS 1: (11-16) Multi-resolution
> AIPS 1: added controls
> AIPS 1: (19) Dynamic range limit
> AIPS 1: (20) Retry factor (see help)
> AIPS 1: NGAUSS 0 Number of resolutions to use
> AIPS 1: WGAUSS *all 0 Resolutions in arc sec >= 0
> AIPS 1: FGAUSS *all 0 Minimum flux for each resol.
> AIPS 1: MAXPIXEL 70000 Maximum pixels searched in
> AIPS 1: each major cycle.
> AIPS 1: DOTV 1 Display residuals on TV ?
> AIPS 1: Start with field = DOTV
> AIPS 1: BADDISK *all 0 Disks to avoid for scratch.
>
>
> as I said above, there is no error or warning message from imagr during
> the cleaning process.
> The stripes appear and become more and more important while the cleaning
> is done.
> (there is no stripe when I use a single field, with normale and MR clean
> process)
>
> There is however a message I don't clearly understand and that comes
> regularly during the cleaning process:
> ALGSTB: Only 635 rows in AP (need 771)
>
> I increased the values of MINPATCH and MAXPIXELS after having this
> message with the default values, but this message is still here.
>
> I am using aips version 31DEC05.
>
> Could you tell me what inputs I should change to get rid of these stripes?
> Or do you think it is due to bad data reduction?
> Also, should I try on a more recent version of aips?
>
> many thanks in advance
>
> Gaelle
>
I don't know how I can help with just this information. There is
nothing in the imaging process which should cause stripes to appear.
I do wonder if 4096x4096 images are correct for your data. (I usually
run SETFC once with IMSIZE and CELLSIZE 0 to find out the image and cell
sizes I should use.) I would recommend using a more modern version of
AIPS - if there is actually a bug the oldest version I will fix is
31DEC07 at this point. The ALGSTB message will go away in modern
versions which adapt the "AP" size to the size of the problems. Do the
stripes start out in a non-central facet? I don't immediately see
anything that should cause trouble.
Eric Greisen
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