[daip] multi-channel continuum calibration

[Eric Greisen]

Farhad Zadeh wrote:
> Hi Eric,
> I am not sure what Doug has done. He may have used miriad (see below) I 
> am all very confused what is the correct way to reduce
> this big data set.
> 
> Thanks.
> Farhad
> 
> 
>  510  TYAPL RELEASE ='31DEC11 '  /********* Start 04-AUG-2011   17:28:10
>    511  TYAPL INNAME='SB4127786   '   INCLASS='UVEVLA'
>    512  TYAPL INSEQ=    1   INDISK=  3
>    513  TYAPL OUTNAME='SB4127786   '   OUTCLASS='TYAPL '
>    514  TYAPL OUTSEQ=    1   OUTDISK=  3
>    515  TYAPL SOURCES = ''    /All sources selected
>    516  TYAPL QUAL     =   -1 CALCODE =
>    517  TYAPL /TIMERANG = beginning to end
>    518  TYAPL STOKES = 'FULL' / Stokes type
>    519  TYAPL BIF =   1, EIF =   2/ IF range
>    520  TYAPL BCHAN =   1, ECHAN =  64/ Chan range
>    521  TYAPL SUBARRAY =   1
>    522  TYAPL / no flagging applied
>    523  TYAPL / no continuum calibration applied
>    524  TYAPL / Weights not calibrated
>    525  TYAPL FRQSEL =    1  / FREQID selected
>    526  TYAPL IN2VERS =    2     / SY file version applied
>    527  FITTP DATAOUT = 'SB4127786' / data written to disk file
>    528  AIPS   IMNAME='SB4127786   ' IMCLASS='TYAPL ' IMSEQ=   1     /
>    529  AIPS   USERNO= 1000            /
>    530    FITS (Flexible Image Transport System) format is defined in 
> 'Astronomy
>    531    and Astrophysics', volume 376, page 359; bibcode: 
> 2001A&A...376..359H
>    532  AIPS   SORT ORDER = 'TB'
>    533        / Where T means TIME (IAT)
>    534        / Where B means BASELINE NUM
>    535  AIPS WTSCAL =  1.00000000000E+00 / CMPLX 
> WTS=WTSCAL*(TAPE*BSCALE+BZERO)
>    536  /End FITS tape header "HISTORY" information
>    537  UVLOD RELEASE= '31DEC11 ' 
> /--------------------------------------------
>    538  UVLOD OUTNAME='DAY0-COR    '   OUTCLASS='TYAPL '
>    539  UVLOD OUTSEQ=    1   OUTDISK=  1
>    540  UVLOD RELEASE= '31DEC11 ' 
> /--------------------------------------------
> 
> 
> On Mon, 8 Aug 2011, Eric Greisen wrote:
> 
>> Farhad Zadeh wrote:
>>> Hi Eric,
>>> We recently observed Sgr A* using EVLA at 7mm in the A-array using
>>> 2x1Ghz band as the headers below show.
>>> We combined the data using avspc and then proceeded  calibrating  the 
>>> data following self-cal (P and A&P)
>>> Turned out the imaging quality is really bad and can't see any 
>>> extended emission except Sgr A*.
>>>
>>> I am suspecting that because of the delay across the
>>> band and the consequent poor  deconvolution that we are getting
>>> terrible images. Any suggestions as to we should proceed properly
>>> (step-by-step including  self-cal on channel data above).
>>>
>>> Many thanks,
>>> Farhad
>>> AIPS 1: Image=MULTI     (UV)         Filename=DAY1-COR    .TYAPL .   1
>>> AIPS 1: Telescope=EVLA               Receiver=EVLA
>>> AIPS 1: Observer=Dr. Farh            User #=  777
>>> AIPS 1: Observ. date=09-JUL-2011     Map date=05-AUG-2011
>>> AIPS 1: # visibilities   3474549     Sort order  TB
>>> AIPS 1: Rand axes: UU-L-SIN  VV-L-SIN  WW-L-SIN  BASELINE  TIME1
>>> AIPS 1:            SOURCE  INTTIM
>>> AIPS 1: ----------------------------------------------------------------
>>> AIPS 1: Type    Pixels   Coord value     at Pixel     Coord incr   Rotat
>>> AIPS 1: COMPLEX      3   1.0000000E+00       1.00  1.0000000E+00    0.00
>>> AIPS 1: STOKES       4  -1.0000000E+00       1.00 -1.0000000E+00    0.00
>>> AIPS 1: FREQ        64   4.1436000E+10       1.00  2.0000000E+06    0.00
>>> AIPS 1: IF           2   1.0000000E+00       1.00  1.0000000E+00    0.00
>>> AIPS 1: RA           1    00 00 00.000       1.00       3600.000    0.00
>>> AIPS 1: DEC          1    00 00 00.000       1.00       3600.000    0.00
>>> AIPS 1: ----------------------------------------------------------------
>>> AIPS 1: Coordinate equinox 2000.00
>>>
>>>
>>> _______________________________________________
>>> Daip mailing list
>>> Daip at listmgr.cv.nrao.edu
>>> http://listmgr.cv.nrao.edu/mailman/listinfo/daip
>>
>> How did you end up with 2 IFs?  This is only 2X128 MHz.
>>
>> Eric
>>

It does look like some of the instructions in the CookBook Appendix E 
were followed (TYAPL) but the HI you sent shows a selection of only 2 
IFs.  You should have had 16!  Perhaps the earlier history would show more.

But for imaging do not run AVSPC.  instead set bchan = 5; echan=59; 
nchav 55; and then run imagr.  You are doing bandwidth synthesis.  But 
Lorant points out that at this frequency in A array you probably will 
not see any extended emission around SgrA*.

Eric Greisen