[daip] More on UVSUB (per L. Kogan's suggestion)
Michael Rupen
mrupen at aoc.nrao.edu
Fri Apr 13 11:36:11 EDT 2001
Dear DAIP,
per Leonia's suggestion, I tried to narrow down the problem using
BCOMP/NCOMP. There are 503 components, all of which PRTCC shows without
any difficulty.
bcomp=1 0 ; ncomp= 1 0 --> DFT, works fine
bcomp=1 0 ; ncomp= 1000 0 --> gridded, fails (same result in OLD=15oct99)
bcomp=1 0 ; ncomp= 500 0 --> gridded, fails
bcomp=1 0 ; ncomp= 50 0 --> DFT, works fine
bcomp=1 0 ; ncomp= 50 0 ; cmethod 'grid' --> gridded, fails
bcomp=1 0 ; ncomp= 1 0 ; cmethod 'grid' --> gridded, fails
bcomp=100 0 ; ncomp= 100 0 ; cmethod 'grid' --> gridded, fails
bcomp=500 0 ; ncomp= 500 0 ; cmethod 'grid' --> gridded, fails
The identical inputs for another image/CC table, created with IMAGR with no
taper/uvrange & a somewhat smaller CELLSIZE & total image area, work
fine. HOWEVER, using another IMAGR made with a different taper but the same
CELLSIZE/image area as the original "problem" image, I get the same errors.
Conclusions:
* this is definitely a problem with gridding (rather than DFTing)
* the problem is reproducible, in that I can create another image
and have the same difficulties
So this must be coming from some difference in the model attached to the
"problem" images. The only obvious thing I can see is that the
"problem" image has CLEAN components further out from the image center,
and centered on 2mas rather than 0.5mas cells. Why this should matter is
beyond me...
Cheerio,
Michael
================================================================================
IMHEAD on "good" image:
AIPS 1: Image=SS433A (MA) Filename=MAR6MERVB W2.ICL001. 1
AIPS 1: Telescope=MERLIN2 Receiver=MERLIN2
AIPS 1: Observer= User #= 213
AIPS 1: Observ. date=06-MAR-1998 Map date=11-APR-2001
AIPS 1: Minimum=-1.09157490E-03 Maximum= 3.44722494E-02 JY/BEAM
AIPS 1: ----------------------------------------------------------------
AIPS 1: Type Pixels Coord value at Pixel Coord incr Rotat
AIPS 1: RA---SIN 4096 19 11 49.570 1894.40 -0.000500 0.00
AIPS 1: DEC--SIN 4096 04 58 57.849 2049.00 0.000500 0.00
AIPS 1: FREQ 1 4.9939999E+09 1.00 1.5000000E+07 0.00
AIPS 1: STOKES 1 1.0000000E+00 1.00 1.0000000E+00 0.00
AIPS 1: ----------------------------------------------------------------
AIPS 1: Coordinate equinox 2000.00
AIPS 1: Map type=NORMAL Number of iterations= 3592
AIPS 1: Conv size= 0.00343 X 0.00182 Position angle= -0.05
AIPS 1: Observed RA 19 09 21.291 DEC 04 53 53.97
AIPS 1: Phase shifted in X -0.077 in Y 0.000
AIPS 1: Rest freq 0.000 Vel type: OPTICAL wrt LSR
AIPS 1: Alt ref. value 0.00000E+00 wrt pixel 1.00
AIPS 1: Maximum version number of extension files of type CC is 2
AIPS 1: Maximum version number of extension files of type HI is 1
AIPS 1: Keyword = 'WTNOISE ' value = 1.141221E+00
AIPS 1: Keyword = 'PARANGLE' value = 3.780212E+01
AIPS 1: Keyword = 'ZENANGLE' value = 9.004292E+01
The two CC tables are the original (CC/1) and a CCEDT'd version (CC/2).
Both work perfectly with UVSUB.
PRTCC on "good" image, CC/1:
MAR6MERVB W2.ICL001. 1 Disk= 5 CC table version 1
Title: AIPS CC CLEAN COMPONENTS TABLE
Created by IMAGR on 11-APR-2001 13:26:37
Last written by IMAGR on 11-APR-2001 13:55:33
Ncomps 3592 sort on: FLUX (FLUX ) (DESCAB)
Comp Delta X Delta Y Flux Total
# Microasec Microasec Jy Jy
1 -54799.98 -5000.00 0.0102907 0.0102907
2 -56299.98 -4500.00 0.0096549 0.0199455
3 -56799.99 -4500.00 0.0093131 0.0292586
4 -60799.99 -3000.00 0.0080977 0.0373563
5 -55799.98 -4500.00 0.0078134 0.0451697
6 -55299.98 -5000.00 0.0039337 0.0491034
7 -52799.98 -5500.00 0.0037670 0.0528704
8 -51299.98 -6000.00 0.0031486 0.0560190
9 -65299.99 -1000.00 0.0029767 0.0589957
10 -61299.99 -2500.00 0.0029045 0.0619002
etc.
IMHEAD on "problem" image:
AIPS 1: Image=SS433A (MA) Filename=MAR6MERVB W2.ICL001. 11
AIPS 1: Telescope=MERLIN2 Receiver=MERLIN2
AIPS 1: Observer= User #= 213
AIPS 1: Observ. date=06-MAR-1998 Map date=11-APR-2001
AIPS 1: Minimum=-4.26457031E-03 Maximum= 1.76580679E-02 JY/BEAM
AIPS 1: ----------------------------------------------------------------
AIPS 1: Type Pixels Coord value at Pixel Coord incr Rotat
AIPS 1: RA---SIN 1024 19 11 49.570 473.60 -0.002000 0.00
AIPS 1: DEC--SIN 1024 04 58 57.849 513.00 0.002000 0.00
AIPS 1: FREQ 1 4.9939999E+09 1.00 1.5000000E+07 0.00
AIPS 1: STOKES 1 1.0000000E+00 1.00 1.0000000E+00 0.00
AIPS 1: ----------------------------------------------------------------
AIPS 1: Coordinate equinox 2000.00
AIPS 1: Map type=NORMAL Number of iterations= 503
AIPS 1: Conv size= 0.02464 X 0.02287 Position angle= -29.41
AIPS 1: Observed RA 19 09 21.291 DEC 04 53 53.97
AIPS 1: Phase shifted in X -0.077 in Y 0.000
AIPS 1: Rest freq 0.000 Vel type: OPTICAL wrt LSR
AIPS 1: Alt ref. value 0.00000E+00 wrt pixel 1.00
AIPS 1: Maximum version number of extension files of type CC is 1
AIPS 1: Maximum version number of extension files of type HI is 1
AIPS 1: Keyword = 'WTNOISE ' value = 1.604667E+00
AIPS 1: Keyword = 'PARANGLE' value = 3.824441E+01
AIPS 1: Keyword = 'ZENANGLE' value = 8.470053E+01
PRTCC on "problem" image, CC/1:
MAR6MERVB W2.ICL001. 11 Disk= 5 CC table version 1
Title: AIPS CC CLEAN COMPONENTS TABLE
Created by IMAGR on 11-APR-2001 16:29:39
Last written by IMAGR on 11-APR-2001 16:35:18
Ncomps 503 sort on: FLUX (FLUX ) (DESCAB)
Comp Delta X Delta Y Flux Total
# Milliasec Milliasec Jy Jy
1 -76.80 -18.00 0.0053710 0.0053710
2 -126.80 34.00 0.0037652 0.0091362
3 -54.80 20.00 0.0028102 0.0119463
4 -56.80 24.00 0.0025450 0.0144913
5 -72.80 -32.00 0.0023453 0.0168365
6 -48.80 16.00 0.0022366 0.0190731
7 -82.80 -18.00 0.0021083 0.0211814
8 -62.80 18.00 0.0020253 0.0232067
9 -68.80 -18.00 0.0019358 0.0251425
10 -56.80 30.00 0.0018540 0.0269964
================================================================================
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