; SETFC ;--------------------------------------------------------------- ;! makes a BOXFILE for input to IMAGR ;# Task Imaging ;----------------------------------------------------------------------- ;; Copyright (C) 1999-2005, 2007-2008 ;; Associated Universities, Inc. Washington DC, USA. ;; ;; This program is free software; you can redistribute it and/or ;; modify it under the terms of the GNU General Public License as ;; published by the Free Software Foundation; either version 2 of ;; the License, or (at your option) any later version. ;; ;; This program is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; ;; You should have received a copy of the GNU General Public ;; License along with this program; if not, write to the Free ;; Software Foundation, Inc., 675 Massachusetts Ave, Cambridge, ;; MA 02139, USA. ;; ;; Correspondence concerning AIPS should be addressed as follows: ;; Internet email: aipsmail@nrao.edu. ;; Postal address: AIPS Project Office ;; National Radio Astronomy Observatory ;; 520 Edgemont Road ;; Charlottesville, VA 22903-2475 USA ;----------------------------------------------------------------------- SETFC LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC SETFC: Task to make a BOXFILE for input to IMAGR INNAME UV dataset name (name) INCLASS UV dataset name (class) INSEQ 0.0 9999.0 UV dataset name (seq. #) INDISK 0.0 9.0 Disk drive # SOURCES Source selected BCOUNT 0.0 511.0 First field number to use BOXFILE disk file to write to (the input BOXFILE for IMAGR) CELLSIZE $ 0.0 (X,Y) size of grid in asec IMSIZE $ 0.0 16384 field size SHIFT Position shift (RA,Dec) asec for all fields FLUX Minimum component flux = (source * beam) BPARM (1) Inner region radius (deg) (2) Field overlap (pixels) (3) Factor to scale NVSS fluxes, 0 -> 1 (4) Radius NVSS search (deg) (5) Flux limit in NVSS (Jy) (6) IMSIZE for NVSS fields (7) IMSIZE for Sun fields (8) Write Clean boxes for NVSS fields (9) Maximum allowed phase error in imaging (10) Points per beaam PBPARM Beam parameters: (1) Cutoff; (2) Use (3)-(7) (3)-(7) Beam shape parms INLIST NVSS input file name ' ' => AIPS provided. NFIELD @ Number fields found ---------------------------------------------------------------- SETFC Type: Task Use: SETFC makes an input BOXFILE to be used as input to IMAGR. It is meant to be used in preparation for wide-field 3D imaging. It prepares BOXFILE data to image an area around the pointing position using a number of overlapped fields. Optionally, it also searches through lists of sources from the NVSS (21 cm VLA D-array) or WENSS/WISH (92 cm Westerbork northern and southern) surveys and adds outlier fields to image those sources above a specified flux limit. It writes an inscribed circular Clean box for the fields covering the primary beam and can, optionally, write small Clean boxes for each of the sources in the outlier fields. The latter will almost certainly require later hand editing but they are instructive. Input adverbs: INNAME......The UV dataset name (name). Standard defaults. INCLASS.....The UV dataset name (class). Standard defaults. INSEQ.......The UV dataset name (seq. #). 0 => highest. INDISK......The disk drive #. 0 => any. SOURCES.....The source to be used from a multi-source file; a single source name is required to get the central pointing position from the source table. Ignored for single-source files. BCOUNT......First field number to use. 0 -> 1. This allows you to append to a pre-existing file with lower field numbers obtained in some other way. BOXFILE.....Output text file containing lines which specify the fields for the multi-field imaging. This file should then be specified as the BOXFILE for IMAGR. If the file already exists, the new information will be appended to it. CELLSIZE....Pixel size for the fields in IMAGR in arc seconds. Value used is returned (i.e. 0's are changed to recommended values) IMSIZE......Size of each field. Value used is returned (i.e. 0's are changed to recommended values) If CELLSIZE and/or IMSIZE are zero, the data are read to find the maximum baseline and maximum W in order to estimate these parameters. The "maximum phase error" in gridding ignoring the W term may be controlled with BPARM(9). SHIFT.......Specifies a position shift in arc seconds at the phase center for all of the fields in the inner portion. The output RA = RA0 + SHIFT(1)/cos(DEC0) and DEC = DEC0 + SHIFT(2) where 0 refers to the input coordinates. FLUX........Minimum included component "flux" = source flux times the single-dish beam power. 0 => any in INLIST meeting BPARM(4). Note, the single dish beam power is taken to be 0.01 outside the main lobe. Fluxes are read from the table, scaled by BPARM(3), and then compared to FLUX. BPARM.......(1) The radius in degrees to be covered fully by overlapping fields. <= 0 means do not do fly's eye list of fields. < 0 => do not include catalog sources within abs (BPARM(1)) of the origin. (2) Field overlap in pixels 0 -> 5. The program now takes into account that the Cleaning area is smaller than the image size since the outer 6 pixels are regarded as unreliable. (3) Factor to scale NVSS fluxes (to account for spectral index on average). 0 -> 1 (4) Radius for the search in the catalog for interfering sources. < BPARM(1) => no search. Try 30 for 74 Mhz imaging. All sources outside the center of the outermost fly's eye field (n.b. < BPARM(1)) and < BPARM(4) are included if they meet the flux criteria. (5) Flux (Jy) limit in catalog search, There are 4 AIPS-provided NVSS files each containing sources > its flux limit. Those limits are 50, 100, 300, and 1000 mJy and searches will be faster if you are just above rather than just below one of these limits. (6) Desired size of external fields; 0 -> 128. (7) Desired size of external fields on Sun; 0 -> 256. (8) > 0 => write Clean boxes in outlier fields. If > 5, use BPARM(8) for the radius in cells. (9) The phase error made in gridding a point is approx 180 * W * (l*l + m*m) degrees where W is in wavelengths and l and m in radians. Thus the maximum field of view (radius) is sqrt(E/(180*Wmax)). BPARM(9) gives the allowed value of E in degrees, where BPARM(9) = 0 -> 45 degrees. The actual value of E used will be reduced by the cos (zenith angle) and will be reduced still further if the average abs(W) > Wmax/4 or the sqrt (average W*W) > Wmax/3. (10) The cell size recommended is 1 / Bmax / Nppb where Bmax is tha maximum baseline and Nppb is the number of points per beam. Even with uniform weighting the beam is often larger than 1/Bmax so one may end up with more than Nppb points per beam. BPARM(10) sets points per beam (when CELLSIZE=0) and 0 -> 3. PBPARM......Primary beam parameters: (1) Lowest beam value to believe: No default. 0.0 => use any beam value (2) > 0 => Use beam parameters from PBPARM(3)-PBPARM(7) Otherwise use default parameters for the VLA (or ATCA where appropriate) (3-7)..For all wavelengths, the beam is described by the function: 1.0 + X*PBPARM(3)/(10**3) + X*X*PBPARM(4)/(10**7) + X*X*X*PBPARM(5)/(10**10) + X*X*X*X*PBPARM(6)/(10**13) X*X*X*X*X*PBPARM(7)/(10**16) where X is (distance from the pointing position in arc minutes times the frequency in GHz)**2. For the VLA, these parms are, by default, given by Perley's fits: 0.0738 GHz -0.897 2.71 -0.242 0.3275 -0.935 3.23 -0.378 1.465 -1.343 6.579 -1.186 4.885 -1.372 6.940 -1.309 8.435 -1.306 6.253 -1.100 14.965 -1.305 6.155 -1.030 22.485 -1.417 7.332 -1.352 43.315 -1.321 6.185 -0.983 For the ATCA, these are by default: 1.5 GHz -1.049 4.238 -0.8473 0.09073 -5.004E-3 2.35 -0.9942 3.932 -0.7772 0.08239 -4.429E-3 5.5 -1.075 4.651 -1.035 0.12274 -6.125E-3 8.6 -0.9778 3.875 -0.8068 0.09414 -5.841E-3 20.5 -0.9579 3.228 -0.3807 0.0 0.0 See explain for details INLIST......Catalog input file name. For format see Explain ' ' => an AIPS-provided files appropriate to BPARM(5): Epoch 2000: FLUX >= 1.000 NV00.1000 ( 2267 objects) FLUX >= 0.300 NV00.0300 ( 14456 objects) FLUX >= 0.100 NV00.0100 ( 63411 objects) FLUX >= 0.030 NV00.0030 (237600 objects) Epoch 1950: FLUX >= 1.000 NV50.1000 ( 2267 objects) FLUX >= 0.300 NV50.0300 ( 14456 objects) FLUX >= 0.100 NV50.0100 ( 63411 objects) FLUX >= 0.030 NV50.0030 (237600 objects) The WENSS/WISH surveys ar also available $AIPSTARS as FLUX >= 0.100 WE00.0100 ( 99709 object 2000) FLUX >= 0.100 WE50.0100 ( 99709 object 1950) Some sites may choose to download really large source lists to deeper flux levels. These may include from the NVSS survey: FLUX >= 0.003 NV00.0003 (1560007 objects, 2000) FLUX >= 0.003 NV50.0003 (1560007 objects, 1950) and the WENSS/WISH survey: FLUX >~ 0.010 WE00.0000 (319770 objects, 2000) FLUX >~ 0.010 WE50.0000 (319770 objects, 1950) These deep files may be particularly useful for BOXES but are too deep to be of much use here. Note: the WENSS survey covers +90 to +28 degrees declination and the WISH survey covers -25 to -15 with some sources to -9. Output adverbs (returned to AIPS): CELLSIZE....Pixel size for the fields in IMAGR in arc seconds. Value used is returned (i.e. 0's are changed to recommended values) IMSIZE......Size of each field. Value used is returned (i.e. 0's are changed to recommended values) NFIELD......Number of fields put in the bOXFILE. ---------------------------------------------------------------- SETFC: Task to make an input BOXFILE to be used with IMAGR DOCUMENTOR: Bryan Butler (NRAO) DESCRIPTION This task was motivated by Lazio & Kassim's SETFAC RUN file which sets facets for wide-field imaging via IMAGR. The original version of the task was then written by Bryan Butler. The purpose of the task is to set up a BOXFILE for input to IMAGR. This is intended to be used for wide-field imaging applications (e.g., VLA 74 MHz data), as a way of specifying multiple fields which cover a wide field of view. It is quite usefull at any wavelength however. The task, if instructed to determine cell and/or image size, will read the UV data to find the maximum baseline and maximum W. The cell size in radians is then 1/Bmax / Nppb where Nppb is the number of points per beam. The formula for phase error which determines the maximum radius of a facet comes from Thompson, Moran, and Swenson, "Interferometry and Synthesis in Radio Astronomy" 2001, pages 73-74. In radians, the facet radius for which all phase errors are less than E degrees is sqrt (E / Wmax / 180). It is found that an error as great as 45 degrees is okay if there are not too many points at large W and if the elevation is not too low. The user may control E with BPARM(9) but the E actually used is set by E = BPARM(9) * cos (ZA) * Wmax / max (Wmax, 4*Wa, 3*Wr) where ZA is the zenith angle at transit, Wa is the average abs(W), and Wr = sqrt (average W*W). This biases things when more than a few points are at large W and reduces the allowed error at low elevations where the results of the phase errors are more serious. The task is split into 2 relatively independent parts. The first is the creation of a "fly's eye" - a tiling of overlapping fields which cover the central part of the primary beam. The second part is the creation of several smaller fields which are centered on NVSS sources and the Sun. The two parts are independent, i.e., you can do either or both of them on any particular run of SETFC. The fly's eye tiling is controlled by the parameters BPARM(1), BPARM(2), CELLSIZE, IMSIZE, and SHIFT. See their description above... The NVSS source catalog is searched within some search radius for sources with flux density greater than specified, and small fields are created around these sources. In order to do this, the position (RA, DEC) of the pointing phase center is required. This is obtained from the input UV data set. In the case of a single-source data set, it is read from the header. In the case of a multi-source data set, the source must be specified in the first element of the adverb SOURCES, and the position is read from the SU extension. The selection of sources is controlled by the adverbs BPARM(4), BPARM(5)< BPARM(6). See their description above. The source catalog may be specified in INLIST or you may use one of the AIPS-provided versions of the NVSS. The format of the file is: All lines beginning with a semi-colon are ignored. They are the copyleft, a descriptive text in the AIPS files, and other comments. Be careful about the epoch of the coordinates. Remaining give the Right ascension in degrees, Declination in degrees, Flux in mJy, and optionally a FWHM in arc seconds using format F9.5,1X,F9.5,I7,F10.4. A sample is given below no width is shown since none are used by SETFC. ;----------------------------------------------------------------------- ; Copyright (C) 1999-2000, 2002 ; Associated Universities, Inc. Washington DC, USA. ; ; This program is free software; you can redistribute it and/or ; modify it under the terms of the GNU General Public License as ; published by the Free Software Foundation; either version 2 of ; the License, or (at your option) any later version. ; ; This program is distributed in the hope that it will be useful, ; but WITHOUT ANY WARRANTY; without even the implied warranty of ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ; GNU General Public License for more details. ; ; You should have received a copy of the GNU General Public ; License along with this program; if not, write to the Free ; Software Foundation, Inc., 675 Massachusetts Ave, Cambridge, ; MA 02139, USA. ; ; Correspondence concerning AIPS should be addressed as follows: ; Internet email: aipsmail@nrao.edu. ; Postal address: AIPS Project Office ; National Radio Astronomy Observatory ; 520 Edgemont Road ; Charlottesville, VA 22903-2475 USA ;----------------------------------------------------------------------- ; NRAO/VLA Sky Survey (NVSS) from CATALOG39.FIT ; 2267 sources brighter than 1.0 Jy ; Catalog made on 1998-07-10 with 1814748 entries ;RA(2000) Dec(2000) Flux ; deg deg mJy 0.08521 55.65239 1518 0.22108 40.90052 1301 0.84166 -17.45316 2415 1.23802 12.80524 1071 1.37727 69.39949 1105 1.55780 -6.39310 2051 1.59416 -0.07363 3898 2.12217 -5.97935 1323 ;..... 358.54728 32.91998 1183 358.59049 45.88455 1873 358.78961 49.83570 2306 358.97312 15.69069 1104 359.25280 -34.75882 1286 359.32748 14.76875 1020 359.38022 -11.42748 1814 359.64781 44.07789 1940 ------------------------------------------------------------ RICK PERLEY'S REPORT - Primary Beam Parameters Polynomial Coefficients from LSq Fit to VLA Primary Beam raster scans. Functional form fitted: 1 + G1.X^2 + G2.X^4 + G3.X^6 where X = r.F, and r = radius in arcminutes F = frequency in GHz. Fits were made to 3% cutoff in power for 24 antennas. Poor fits, and discrepant fits were discarded, and the most consistent subset of antennas had their fitted coefficients averaged to produce the following 'best' coefficients. Freq. G1 G2 G3 ---------------------------------------------------------- 0.0738 -0.897E-3 2.71 E-7 -0.242E-10 0.3275 -0.935 3.23 -0.378 1.285 -1.329 6.445 -1.146 * 1.465 -1.343 6.579 -1.186 4.885 -1.372 6.940 -1.309 8.435 -1.306 6.253 -1.100 14.965 -1.305 6.155 -1.030 22.485 (old) -1.350 6.526 -1.090 * 22.485 (new) -1.417 7.332 -1.352 43.315 -1.321 6.185 -0.983 ----------------------------------------------------------- The estimated errors (from the scatter in the fitted coefficients) are generally very small: G1: .003 at all bands except Q (.014) G2: .03 to .07 at all bands except Q (.15) G3: .01 to .02 at all bands except Q (.04) R. Perley 21/Nov/00 * The 1.285 and 22.485 old feed values are not used.