I have encountered a weird problem using multi-resolution clean on a calibrator for my M87 movie project. I only just started using a second resolution on this pass of processing, but I am now trying to automate a process I had done before. On the earlier effort, last September, I had used 2 resolutions with reasonable results. I have also used multi-resolution clean on another project since then without trouble. The problem is that, after many iterations at the full resolution, IMAGR settles into a pattern of major cycles on the second field which just repeat over and over. The CCs get added to the CC table, but apparently don't get subtracted from the UV data. It keeps going until the iteration limit is reached, whereupon it compresses over 4000 components into 9! The residual image looks like it has just started to work on the region where it is allowed to find components. The restored first field image has a huge amount of flux (much more than in the bright core) in the outer, nominally very weak, components where the second resolution was allowed to work. If I kill IMAGR before it compresses the components, I find the CC table is many repeats of the following group of 12 (except the first 12 which are very slightly different - I think there was one more pass at field 1 after that). This is all consistent with my speculation above that the components are not being subtracted in the major cycle, but are being added to the CC table. 37 -3290.00 -2275.00 500.00 500.00 .0 Gaus .009606 .240402 38 -3290.00 -2275.00 500.00 500.00 .0 Gaus .008645 .249047 39 -3290.00 -2275.00 500.00 500.00 .0 Gaus .007781 .256828 40 -3290.00 -2240.00 500.00 500.00 .0 Gaus .007004 .263832 41 -5145.00 -3605.00 500.00 500.00 .0 Gaus .006325 .270157 42 -3290.00 -2240.00 500.00 500.00 .0 Gaus .006287 .276445 43 -5145.00 -3605.00 500.00 500.00 .0 Gaus .005677 .282121 44 -3360.00 -2415.00 500.00 500.00 .0 Gaus .005658 .287780 45 -3150.00 -2030.00 500.00 500.00 .0 Gaus .005268 .293047 46 -5145.00 -3605.00 500.00 500.00 .0 Gaus .005081 .298128 47 -3395.00 -2730.00 500.00 500.00 .0 Gaus .004914 .303042 48 -3115.00 -1995.00 500.00 500.00 .0 Gaus .004601 .307643 Here are the IMAGR inputs: >inp AIPS 1: IMAGR: Wide field imaging/Clean task AIPS 1: Adverbs Values Comments AIPS 1: ---------------------------------------------------------------- AIPS 1: INNAME 'BW082BS3C279' Input UV data (name) AIPS 1: INCLASS 'CALIB' Input UV data (class) AIPS 1: INSEQ 31 Input UV data (seq. #) AIPS 1: INDISK 3 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: ANTENNAS *all 0 Antennas to plot AIPS 1: BASELINE *all 0 Baselines with ANTENNAS AIPS 1: DOCALIB -1 > 0 calibrate data & weights AIPS 1: > 99 do NOT 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 'BW082BS3C279' Output image name (name) AIPS 1: OUTDISK 3 Output image disk drive # AIPS 1: OUTSEQ 31 Output seq. no. AIPS 1: OUTVER 0 CC ver. no (Continuum only) AIPS 1: *** SET OUTVER ON RESTARTS AIPS 1: IN2NAME 'BW082BS3C279' UV work file name AIPS 1: IN2CLASS 'UVWORK' UV work file class AIPS 1: IN2SEQ 31 UV work file seq AIPS 1: *** SET TO KEEP WORK FILE AIPS 1: IN2DISK 3 UV work file disk AIPS 1: CELLSIZE 3.500E-05 3.500E-05 (X,Y) size of grid in asec AIPS 1: IMSIZE 512 512 Minimum image size AIPS 1: NFIELD 1 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 1000000 500000 (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 14.18 0 0-spacing fluxes and weights AIPS 1: 0 0 SEE HELP!! AIPS 1: 8.400E-04 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 .5 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 5000 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 'BW082BS:BW082BS_3C279_ Input file of field params AIPS 1: BOX1' AIPS 1: and Clean boxes; ' ' => use AIPS 1: FLDSIZE, RASHIFT, DECSHIFT, AIPS 1: NBOXES, CLBOX only. AIPS 1: OBOXFILE *all ' ' Output file for final Clean AIPS 1: boxes AIPS 1: GAIN .1 Clean loop gain AIPS 1: FLUX 0 Minimum Clean component (Jy) AIPS 1: MINPATCH 128 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 0 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 0 0 Task enrichment parameters AIPS 1: 0 0 (1) Antenna diameter (m) AIPS 1: 0 0 (2) Source Spectral index AIPS 1: 0 0 (3) Frequency scaling factor AIPS 1: 0 2 (4) > 0 -> SDI Clean factor AIPS 1: 1 .03 (5) >0 => scale residuals AIPS 1: 1.000E-05 .01 (6) Half-width in x of box AIPS 1: *rest 0 (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: (17) spectral index radius AIPS 1: 0 -> no correction AIPS 1: (19) Dynamic range limit AIPS 1: (20) Retry factor (see help) AIPS 1: NGAUSS 2 Number of resolutions to use AIPS 1: WGAUSS 0 5.000E-04 Resolutions in arc sec >= 0 AIPS 1: *rest 0 AIPS 1: FGAUSS .0018 .004 Minimum flux for each resol. AIPS 1: *rest 0 AIPS 1: MAXPIXEL 20000 Maximum pixels searched in AIPS 1: each major cycle. AIPS 1: IN3NAME ' ' Spectral index image name AIPS 1: IN3CLASS ' ' Spectral index image class AIPS 1: IN3SEQ 0 Spectral index image sequence AIPS 1: number AIPS 1: IN3DISK 0 Spectral index image disk AIPS 1: IN4NAME ' ' Spectral curvature name AIPS 1: IN4CLASS ' ' Spectral curvature class AIPS 1: IN4SEQ 0 Spectral curvature sequence AIPS 1: number AIPS 1: IN4DISK 0 Spectral curvature disk AIPS 1: FQTOL -1 Frequency tolerance in kHz AIPS 1: (primary beam & spec index) AIPS 1: DOTV -1 Display residuals on TV ? AIPS 1: Start with field = DOTV AIPS 1: GRCHAN 0 Graphics channel of boundary AIPS 1: BADDISK *all 0 Disks to avoid for scratch. Here is an IMH of the uv data: AIPS 1: Image=3C279 (UV) Filename=BW082BS3C279.CALIB . 31 AIPS 1: Telescope=VLBA Receiver=VLBA AIPS 1: Observer=BW082 User #= 450 AIPS 1: Observ. date=11-APR-2006 Map date=19-FEB-2007 AIPS 1: # visibilities 56086 Sort order TB AIPS 1: Rand axes: UU-L-SIN VV-L-SIN WW-L-SIN TIME1 BASELINE AIPS 1: INTTIM GATEID CORR-ID WEIGHT SCALE AIPS 1: ---------------------------------------------------------------- AIPS 1: Type Pixels Coord value at Pixel Coord incr Rotat AIPS 1: COMPLEX 1 1.0000000E+00 1.00 1.0000000E+00 .00 AIPS 1: STOKES 4 -1.0000000E+00 1.00 -1.0000000E+00 .00 AIPS 1: FREQ 1 4.3131459E+10 1.00 7.0000000E+06 .00 AIPS 1: IF 2 1.0000000E+00 1.00 1.0000000E+00 .00 AIPS 1: RA 1 12 56 11.167 1.00 3600.000 .00 AIPS 1: DEC 1 -05 47 21.525 1.00 3600.000 .00 AIPS 1: ---------------------------------------------------------------- AIPS 1: Coordinate equinox 2000.00 AIPS 1: Rest freq .000 Vel type: OPTICAL wrt YOU AIPS 1: Alt ref. value 0.00000E+00 wrt pixel .00 AIPS 1: Maximum version number of extension files of type FQ is 1 AIPS 1: Maximum version number of extension files of type HI is 1 AIPS 1: Maximum version number of extension files of type OB is 1 AIPS 1: Maximum version number of extension files of type AN is 1 AIPS 1: Maximum version number of extension files of type FG is 2 AIPS 1: Maximum version number of extension files of type WX is 1 Here is the boxfile. Note that the clean regions for the 2 resolutions don't overlap. The first time the problem appeared, field 2 was allowed to get at the central regions also so there was overlap. # FILEBOX: 04-FEB-2007 22:26:50 # FILEBOX: 19-FEB-2007 12:47:56 # FILEBOX: 19-FEB-2007 12:48:08 # FILEBOX: 19-FEB-2007 13:37:01 # FILEBOX: 19-FEB-2007 13:37:43 1 -1 17 260 250 1 -1 16 271 240 1 -1 9 257 267 1 -1 15 285 227 # FILEBOX: 19-FEB-2007 13:38:00 2 -1 59 370 179 I am running on my Apple PowerBook G4. After originally encountering the problem, I ran the midnight job to be sure I had the latest version of the program. That did not help. ---------------------------- There is another issue I noticed while doing all this. The CC table records components of the size requested in WGAUSS even if the actual fitted size turns out to be very different. For example, when I request a second image with a resolution of 0.00045 arcsec, I get a fitted beam of .00088 X .00061 arcsec, which is much larger. My first field fitted beam is .00061 X .00023 so I am not asking for a big change (although I first tried for 0.0005, and reduced it to try to get a smaller fitted beam). Clearly the algorithm for how to taper the data for the requested beam is not working too well on highly centrally condensed data and not a big reduction in beam size. The net effect, since I have no control over this, is that I'm being forced to superresolve my second resolution image. I'd suggest several possible alternative actions: 1. Iterate the tapers until the fitted beam is closer to the requested beam. 2. Use the fitted beam in the CCs and restoration. 3. Allow the taper to be specified instead of the beam size.