[daip] IMAGR 2006 vs. 2007; filtering of CCs

[Lynn D. Matthews]

In doing some benchmarking tests today, I discovered that the images I
create with the 2006 vs. 2007 versions of AIPS are not identical. The AIPS
Newletter mentioned that some differences might be expected depending on
the AP size used. However, the most drastic difference occurs when
filtering of clean components is used. In this case, the resulting Flux
density is significantly different in the 2007 AIPS compared with all
other cases.

Here are some sample "IMSTATs" for the same data, imaged five times:

31DEC06, filtering of CCs; AP=20

AIPS 2: Mean= 3.1993E-06 rms= 8.0895E-03 JY/BEAM   over67108864. pixels
AIPS 2: Maximum= 2.7252E-01 at  5749  5528    1    1    1    1    1
AIPS 2: Skypos: RA 05 35 14.50751965  DEC -05 22 30.573064
AIPS 2: Skypos: IPOL  42816.341 MHZ
AIPS 2: Minimum=-5.1576E-02 at 7648 4154    1    1    1    1    1
AIPS 2: Skypos: RA 05 35 14.50116169  DEC -05 22 30.641764
AIPS 2: Skypos: IPOL  42816.341 MHZ
AIPS 2: Flux density =  3.7519E+00 Jy.   Beam area =  57.23 pixels

31DEC06, filtering of CCs; AP=80

AIPS 2: Mean= 3.0773E-06 rms= 8.0910E-03 JY/BEAM   over67108864. pixels
AIPS 2: Maximum= 2.7080E-01 at  5748  5527    1    1    1    1    1
AIPS 2: Skypos: RA 05 35 14.50752286  DEC -05 22 30.573117
AIPS 2: Skypos: IPOL  42816.341 MHZ
AIPS 2: Minimum=-5.1691E-02 at 7648 4154    1    1    1    1    1
AIPS 2: Skypos: RA 05 35 14.50116156  DEC -05 22 30.641767
AIPS 2: Skypos: IPOL  42816.341 MHZ
AIPS 2: Flux density =  3.6088E+00 Jy.   Beam area =  57.23 pixels

31DEC06, no filtering of CCs; AP=20

AIPS 2: Mean= 3.1996E-06 rms= 8.0887E-03 JY/BEAM   over67108864. pixels
AIPS 2: Maximum= 2.7254E-01 at  5749  5528    1    1    1    1    1
AIPS 2: Skypos: RA 05 35 14.50751965  DEC -05 22 30.573064
AIPS 2: Skypos: IPOL  42816.341 MHZ
AIPS 2: Minimum=-5.1573E-02 at 7648 4154    1    1    1    1    1
AIPS 2: Skypos: RA 05 35 14.50116169  DEC -05 22 30.641764
AIPS 2: Skypos: IPOL  42816.341 MHZ
AIPS 2: Flux density =  3.7522E+00 Jy.   Beam area =  57.23 pixels

31DEC07, filtering of CCs

AIPS 2: Mean= 4.7491E-06 rms= 8.3291E-03 JY/BEAM   over67108864. pixels
AIPS 2: Maximum= 2.7672E-01 at  5749  5528    1    1    1    1    1
AIPS 2: Skypos: RA 05 35 14.50751965  DEC -05 22 30.573064
AIPS 2: Skypos: IPOL  42816.341 MHZ
AIPS 2: Minimum=-5.3621E-02 at 7648 4154    1    1    1    1    1
AIPS 2: Skypos: RA 05 35 14.50116169  DEC -05 22 30.641764
AIPS 2: Skypos: IPOL  42816.341 MHZ
AIPS 2: Flux density =  5.5693E+00 Jy.   Beam area =  57.23 pixels

31DEC07, no filtering of CCs

AIPS 2: Mean= 3.1049E-06 rms= 8.0916E-03 JY/BEAM   over67108864. pixels
AIPS 2: Maximum= 2.7394E-01 at  5749  5528    1    1    1    1    1
AIPS 2: Skypos: RA 05 35 14.50751965  DEC -05 22 30.573064
AIPS 2: Skypos: IPOL  42816.341 MHZ
AIPS 2: Minimum=-5.1233E-02 at 8185 2208    1    1    1    1    1
AIPS 2: Skypos: RA 05 35 14.49936379  DEC -05 22 30.739064
AIPS 2: Skypos: IPOL  42816.341 MHZ
AIPS 2: Flux density =  3.6412E+00 Jy.   Beam area =  57.23 pixels