[daip] Possible BUG in AIPS task CHKFC

[Subhashis Roy]

Hi,

I tried to use CHKFC to find out the Fields which will contain certain
sources.

However, I find that CHKFC gives a message.
-------
localh> CHKFC1: ZTXOP2: /export/astron/roy/GC250.IMAGR.FIN
localh> CHKFC1: I DO NOT HANDLE TYPE 'C' LINES IN BOXFIL
localh> CHKFC1: I DO NOT HANDLE TYPE 'C' LINES IN BOXFIL
localh> CHKFC1: I DO NOT HANDLE TYPE 'C' LINES IN BOXFIL
localh> CHKFC1: I DO NOT HANDLE TYPE 'C' LINES IN BOXFIL
-------------

However, it puts the following parameters in the message file.

--------------
localh> CHKFC1: FIELDF: Final field parameters and # read are:
localh> CHKFC1: Field  1  250  250  266.43012  -29.00554
localh> CHKFC1: Field  2    0    0    0.00000    0.00000
localh> CHKFC1: Field  3    0    0    0.00000    0.00000
localh> CHKFC1: Field  4    0    0    0.00000    0.00000
-----------------------

My input BOXFILE contains 82 lines. The first 4 lines are:

--------
C 1 250 250 17 45 43.23 -29 00 19.940
F 2 250 250 -200 870
F 3 250 250 -200 1920
F 4 250 250 -200 2970
------------

While I looked at the header of the out files, except the first one,
others have a central co-ordinate of RA 00 00 00 and DEC 00 00 00.

--------------
AIPS 1: Image=TESTFACE  (MA)         Filename=SAGA.250CHK .IIM002.   1
AIPS 1: Telescope=AIPS               Receiver=
AIPS 1: Observer=CHKFC               User #=  140
AIPS 1: Observ. date=BAD DATE        Map date=16-NOV-2005
AIPS 1: Pixel type: FLOATING         Magic value blanking
AIPS 1: Minimum= 0.00000000E+00      Maximum= 3.00000000E+00 JY/BEAM
AIPS 1: ----------------------------------------------------------------
AIPS 1: Type    Pixels   Coord value     at Pixel     Coord incr   Rotat
AIPS 1: RA---SIN   256    00 00 00.000     128.00         -4.200    0.00
AIPS 1: DEC--SIN   256    00 00 00.000     129.00          4.200    0.00
AIPS 1: ----------------------------------------------------------------
AIPS 1: Coordinate equinox 2000.00
AIPS 1: Maximum version number of extension files of type HI is   1
-----------------------

The input parameters were:
------------------------
AIPS 1: CHKFC:  Makes images showing the fields and boxes in BOXFILE
AIPS 1: Adverbs     Values                 Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: OUTNAME    'SAGA.250CHK '          Output Image name (name)
AIPS 1: OUTSEQ        0                    Output Image name (seq. #)
AIPS 1: OUTDISK       5                    Disk drive #
AIPS 1: BOXFILE    '/export/astron/roy/GC250.IMAGR.FIN              '
AIPS 1:                                    disk file to read field locs
AIPS 1:                                    and Clean boxes
AIPS 1: CELLSIZE      4.2         4.2      (X,Y) size of grid in asec
AIPS 1: IMSIZE      250         250        field size
AIPS 1: SHIFT         0           0        Position shift (RA,Dec) asec
AIPS 1:                                    for all fields
AIPS 1: DOBLANK       1                    > 0 Use blanks for unCleaned
AIPS 1: DOWEDGE       2                    > 0 Add field number in boxes
-------------------

Since the Explain file of this task do not mention anything particular
about the input format, I assume it follows the same convention of
IMAGR.
Therefore, as it do not understand the IMAGR BOXFILE, it is a BUG. 

(It does not even produce any output file, if there is no line
containing 'C' in the BOXFILE).

As I understand, mixing 'C' and 'F' could result in contradicting
situations (unless it can read the header from some file), but I believe
that as long as each of the 'F' fields have different offsets, it should
be able to put different RA and DEC in the output (it could assume an
user supplied central RA and DEC).

I am using 31DEC04 version of AIPS.

Thanks.
Subhashis