o-smirnov
commented
8 years ago What's your weighting? It's not clear to me what weighting was used to derive the numbers on the NRAO site you link to, either.
On Mon, May 2, 2016 at 1:37 PM, Modhurita Mitra notifications@github.com wrote:
I simulated an MS with the following command:
simms -T vla-b -t ascii -cs itrf -dec 35d56m9.29s -ra 2h21m3.73s -st 6 -dt 10 -f0 1.4649GHz -nc 1 -df 50MHz -date J2000,1998/08/31
(The -t ascii -cs itrf part is probably redundant, as vla-b is one of the antenna configurations simms knows about)
Then I populated it with visibilities using a model file in meqtrees. I imaged the MS with the following wsclean command:
wsclean -niter 10000 -scale 0.75asec -name einstein_ring_4Jy -datacolumn CORRECTED_DATA -field 0 -pol IQUV -gain 0.1 -threshold 2e-04 -size 64 64 vla_6h10s.MS
Here is the header of the resultant image fits file:
SIMPLE = T / file does conform to FITS standard BITPIX = -32 / number of bits per data pixel NAXIS = 4 / number of data axes NAXIS1 = 64 / length of data axis 1 NAXIS2 = 64 / length of data axis 2 NAXIS3 = 1 / length of data axis 3 NAXIS4 = 1 / length of data axis 4 EXTEND = T / FITS dataset may contain extensions COMMENT FITS (Flexible Image Transport System) format is defined in 'Astronomy COMMENT and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H BSCALE = 1. BZERO = 0. BUNIT = 'JY/BEAM ' / Units are in Jansky per beam BMAJ = 0.000790675608255723 BMIN = 0.000695242607818782 BPA = 63.6616846018877 EQUINOX = 2000. / J2000 BTYPE = 'Intensity' ORIGIN = 'WSClean ' / W-stacking imager written by Andre Offringa CTYPE1 = 'RA---SIN' / Right ascension angle cosine CRPIX1 = 33. CRVAL1 = 35.26554 CDELT1 = -0.0002083333 CUNIT1 = 'deg ' CTYPE2 = 'DEC--SIN' / Declination angle cosine CRPIX2 = 33. CRVAL2 = 35.93591 CDELT2 = 0.0002083333 CUNIT2 = 'deg ' CTYPE3 = 'FREQ ' / Central frequency CRPIX3 = 1. CRVAL3 = 1464900000. CDELT3 = 0. CUNIT3 = 'Hz ' CTYPE4 = 'STOKES ' CRPIX4 = 1. CRVAL4 = 1. CDELT4 = 1. CUNIT4 = ' ' SPECSYS = 'TOPOCENT' DATE-OBS= '1998-08-31T10:56:11.4' WSCDATAC= 'CORRECTED_DATA' WSCWEIGH= 'uniform ' WSCFIELD= 0. WSCGAIN = 0.1 WSCGKRNL= 7. WSCIMGWG= 214.000000000355 WSCMAJOR= 1. WSCMGAIN= 1. WSCMINOR= 2292. WSCNEGCM= 1. WSCNEGST= 0. WSCNITER= 10000. WSCNWLAY= 32. WSCTHRES= 0.0002
The resolution of this image (calculated as √(BMAJ x BMIN)) is 2.67 arcsec, but the L-band resolution of the VLA at B configuration is supposed to be 4.3 arcsec https://science.nrao.edu/facilities/vla/docs/manuals/oss/performance/resolution .
Any idea where this might be going wrong? Since the resolution is related to antenna positions, I am thinking it might be something to do with the vla-b antenna positions read in by simms.
— You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub https://github.com/radio-astro/simms/issues/31
modhurita
SpheMakh
I simulated an MS with the following command:
simms -T vla-b -t ascii -cs itrf -dec 35d56m9.29s -ra 2h21m3.73s -st 6 -dt 10 -f0 1.4649GHz -nc 1 -df 50MHz -date J2000,1998/08/31(The
-t ascii -cs itrfpart is probably redundant, as vla-b is one of the antenna configurations simms knows about)Then I populated it with visibilities using a model file in meqtrees. I imaged the MS with the following wsclean command:
wsclean -niter 10000 -scale 0.75asec -name einstein_ring_4Jy -datacolumn CORRECTED_DATA -field 0 -pol IQUV -gain 0.1 -threshold 2e-04 -size 64 64 vla_6h10s.MSHere is the header of the resultant image fits file:
The resolution of this image (calculated as √(BMAJ x BMIN)) is 2.67 arcsec, but the L-band resolution of the VLA at B configuration is supposed to be 4.3 arcsec.
Any idea where this might be going wrong? Since the resolution is related to antenna positions, I am thinking it might be something to do with the vla-b antenna positions read in by
simms.