; BCHAN
;---------------------------------------------------------------
;! sets the beginning channel number
;# ADVERB SPECTRAL
;-----------------------------------------------------------------------
;;  Copyright (C) 1995, 2020
;;  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
;-----------------------------------------------------------------------
;---------------------------------------------------------------
BCHAN     LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC
----------------------------------------------------------------
BCHAN
Type:  Adverb  (scalar)
Use:   To set a beginning "channel" number, where the
       definition of channel will depend on the particular
       verb or task.
Null value:
       0   => 1.
Verbs:
   OBITIMAG......Access to OBIT task Imager without self-cal or peeling.
   OBITMAP.......Simplified access to OBIT task Imager.
   OBITPEEL......Access to OBIT task Imager with self-cal and peeling.
   OBITSCAL......Access to OBIT task Imager with self-cal, NOT peeling.
   REMOVIE.......Verb to rerun a previously loaded (TVMOVIE) movie.
Procedures:
   CXIMAGR.......Grid UV data into a complex image, Fourier transform,
                 Clean.
   CXPOLN........Procedure to make complex polarization images and beam.
   FXALIAS.......Least squares fit aliasing function and remove.
   IMFRING.......Large image delay fitting with IM2CC and OOFRING.
   LINIMAGE......Build image cube from multi-IF data set.
   MAPPR.........Simplified access to IMAGR.
   OOFRING.......Fringe fit data to determine calibration with spectral
                 index options.
   PEELR.........Calibrates interfering sources in multi-facet imges.
   VLBAFRGP......Fringe fit phase referenced data and apply calibration.
   VLBAFRNG......Fringe fit data and apply calibration.
   VLBAKRGP......Fringe fit phase referenced data and apply calibration.
   VLBAKRNG......Fringe fit data and apply calibration.
   VLBAMPCL......Calculates and applies manual instrumental phase
                 calibration.
Tasks:
   ACFIT.........Determine antenna gains from autocorrelations.
   ACLIP.........Edits suto-corr data for amplitudes, phases, and weights
                 out of range.
   ALVAR.........Plots the Allan Variance statistic of a UV data set.
   ALVPR.........Prints statistics on the Allan Variance of a UV data set.
   ANBPL.........Plots and prints uv data converted to antenna based
                 values.
   BLANK.........Blanks out selected, e.g. non-signal, portions of an
                 image.
   BLAVG.........Average cross-polarized UV data over baselines.
   BLING.........Find residual rate and delay on individual baselines.
   BLSUM.........Sums images over irregular sub-images, displays spectra.
                 BCHAN is the plane in the blotch image to be used.
   BPEPL.........Plots bandpass tables overlaying multiple times like
                 BPEDT.
   BPFLG.........Flgas uv data based on bad BP values.
   BPLOT.........Plots bandpass tables in 2 dimensions as function of
                 time.
   BPSMO.........Smooths or interpolates bandpass tables to regular times.
   BPWGT.........Calibrates data and scales weights by bandpass
                 correction.
   BSCAN.........Seeks best scan to use for phase cal, fringe search, ..
   BSTST.........Graphical display of solutions to frequency-switched
                 data.
   CAPLT.........Plots closure amplitude and model from CC file.
   CLIP..........Edits data based on amplitudes, phases, and weights out
                 of range.
   CLPLT.........Plots closure phase and model from CC file.
   COHER.........Baseline Phase coherence measurement.
   CORER.........Calculates correlator statistics and flags bad ones.
   CPASS.........Computes polynomial spectral bandpass correction table.
   DECOR.........Measures the decorrelation between channels and IF of uv
                 data.
   DFTIM.........Makes image of DFT at arbitrary point showing time vs
                 frequency.
   DFTPL.........Plots DFT of a UV data set at arbitrary point versus
                 time.
   DIFRL.........Divides the RR data by LL data.
   DTSUM.........Task to provide a summary of the contents of a dataset.
   EDITR.........Interactive baseline-oriented visibility editor using the
                 TV.
   EVAUV.........Subtracts & divides a model into UV data, does statistics
                 on results.
   FGCNT.........Counts samples comparing two flag tables.
   FGPLT.........Plots selected contents of FG table.
   FGPRT.........Pprints counts of selected portions of an FG table.
   FGSPW.........Flags bad spectral windows.
   FILLM.........Reads VLA on-line/archive format uv data tapes (post Jan
                 88).
   FINDR.........Find normal values for a uv data set.
   FITLD.........Reads FITS files to load images or UV (IDI or UVFITS)
                 data to disk.
   FIXAL.........Least squares fit aliasing function and remove.
   FIXWT.........Modify weights to reflect amplitude scatter of data.
   FLAGR.........Edit data based on internal RMS, amplitudes, weights.
   FLGIT.........Flags data based on the rms of the spectrum.
   FRING.........Fringe fit data to determine antenna calibration, delay,
                 rate.
   FRMAP.........Task to build a map using fringe rate spectra.
   FRPLT.........Task to plot fringe rate spectra.
   FTFLG.........Interactive flagging of UV data in channel-time using the
                 TV.
   FUDGE.........Modifies UV data with user's algorithm: paraform task.
   IBLED.........Interactive BaseLine based visibility EDitor.
   IMAGR.........Wide-field and/or wide-frequency Cleaning / imaging task.
   KRING.........Fringe fit data to determine antenna calibration, delay,
                 rate.
   LISTR.........Prints contents of UV data sets and assoc. calibration
                 tables.
   LPCAL.........Determines instrumental polarization for UV data.
   MORIF.........Combines IFs or breaks spectral windows into multiple
                 windows (IFs).
   NOIFS.........Makes all IFs into single spectrum.
   OMFIT.........Fits sources and, optionally, a self-cal model to uv
                 data.
   OTFUV.........Translates on-the-fly single-dish SDD format to AIPS UV
                 file.
   PCPLT.........Plots pulse-cal tables in 2 dimensions as function of
                 time.
   PDPLT.........Plots selected contents of PD tables.
   PLOTC.........Plots color schems used by 3-color plot tasks.
   POSSM.........Task to plot total and cross-power spectra.
   REIFS.........Breaks spectral windows into multiple spectral windows
                 (IFs).
   RFI...........Look for RFI in uv data.
   RLDIF.........Determines Right minus Left phase difference, corrects
                 cal files.
   RLDLY.........Fringe fit data to determine antenna R-L delay
                 difference.
   SBCOR.........Task to correct VLBA data for phase shift between USB &
                 LSB.
   SDCAL.........Task to apply single dish calibration.
   SDGRD.........Task to select and image random-position single-dish
                 data.
   SDIMG.........Task to select and image random-position single-dish
                 data.
   SDMOD.........Modifies single-dish UV data with model sources.
   SERCH.........Finds line signals in transposed data cube.
   SHOUV.........Displays uv data in various ways.
   SNP2D.........Task to convert SN table single-channel phase to delay.
                 BCHAN is the channel that was used in CALIB.
   SPCAL.........Determines instrumental polzn. for spec. line UV data.
   SPFLG.........Interactive flagging of UV data in channel-TB using the
                 TV.
   SPLAT.........Applies calibration and splits or assemble selected
                 sources.
   SPLIT.........Converts multi-source to single-source UV files w
                 calibration.
   SPMOD.........Modify UV database by adding a model with spectral lines.
   SPRMS.........Plots spectral statistics of a selected subset of a uv
                 data set.
   SUFIX.........Modifies source numbers on uv data.
   TI2HA.........Modifies times in UV data to hour angles.
   TIORD.........Checks data for time baseline ordering, displays
                 failures.
   TRUEP.........Determines true antenna polarization from special data
                 sets.
   TVFLG.........Interactive flagging of UV data using the TV.
   UFLAG.........Plots and edits data using a uv-plane grid and the TV.
   UV2MS.........Append single-source file to multi-source file.
   UV2TB.........Converts UV autocorrelation spectra to tables.
   UVAVG.........Average or merge a sorted (BT, TB) uv database.
   UVBAS.........Averages several channels and subtracts from uv data.
   UVCOP.........Task to copy a subset of a UV data file.
   UVCRS.........Finds the crossing points of UV-ellipses.  BCHAN is the
                 channel number in the visibility data set to be used.
   UVDEC.........Decrements the number of spectral channels, keeping every
                 nth.
   UVFIT.........Fits source models to uv data.
   UVFLG.........Flags UV-data.
   UVFND.........Prints selected data from UV data set to search for
                 problems.
   UVGIT.........Fits source models to uv data.
   UVHGM.........Plots statistics of uv data files as histogram.
   UVHIM.........Makes image of the histogram on two user-chosen axes.
   UVIMG.........Grid UV data into an "image".
   UVLSD.........Least squares fit to channels and divides the uv data.
   UVLSF.........Least squares fit to channels and subtracts from uv data.
   UVMOD.........Modify UV database by adding a model incl spectral index.
   UVPLT.........Plots data from a UV data base in multiple ways.
   UVRFI.........Mitigate RFI by Fourier transform or fitting the circle.
   UVRMS.........Computes statistics of a selected subset of a uv data
                 set.
   VLBIN.........Task to read VLBI data from an NRAO/MPI MkII correlator.
   VPFLG.........Resets flagging to all or all corss-hand whenever some
                 are flagged.
   VPLOT.........Plots uv data and model from CC file.
   WIPER.........Plots and edits data from a UV data base using the TV.
   XYDIF.........Find/apply X minus Y linear polarization phase
                 difference.
   XYMOD.........Compute linear polarization point source model, applies
                 to data.
----------------------------------------------------------------
