[daip] 1983 data header

[Harriet Cullen]

Dear Eric

I am very sorry - i sent you the header of a cleaned image by mistake.
Here is the header for the uv data

AIPS 1: Image=MULTI     (UV)         Filename=A116LINE_2  .LINE  .   1
AIPS 1: Telescope=VLA                Receiver=VLA
AIPS 1: Observer=AK89                User #=  892
AIPS 1: Observ. date=17-JUL-1983     Map date=07-JUL-2003
AIPS 1: # visibilities     63042     Sort order  TB
AIPS 1: Rand axes: UU-L-SIN  VV-L-SIN  WW-L-SIN  BASELINE  TIME1
AIPS 1:            SOURCE  FREQSEL  WEIGHT  SCALE
AIPS 1: ----------------------------------------------------------------
AIPS 1: Type    Pixels   Coord value     at Pixel     Coord incr   Rotat
AIPS 1: COMPLEX      1   1.0000000E+00       1.00  1.0000000E+00    0.00
AIPS 1: FREQ        31   1.4136972E+09      64.00  4.8828125E+04    0.00
AIPS 1: STOKES       1  -1.0000000E+00       1.00 -1.0000000E+00    0.00
AIPS 1: IF           1   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    0.00
AIPS 1: Maximum version number of extension files of type FQ is   1
AIPS 1: Maximum version number of extension files of type HI is   1
AIPS 1: Maximum version number of extension files of type WX is   1
AIPS 1: Maximum version number of extension files of type AN is   1
AIPS 1: Maximum version number of extension files of type CL is   2
AIPS 1: Maximum version number of extension files of type SU is   1
AIPS 1: Maximum version number of extension files of type TY is   1
AIPS 1: Maximum version number of extension files of type NX is   1
AIPS 1: Maximum version number of extension files of type FG is   1
AIPS 1: Maximum version number of extension files of type BP is   1
AIPS 1: Keyword = 'OBSCHANS'  value =           32
AIPS 1: Keyword = 'CORRMODE'  value = '1A      '
AIPS 1: Keyword = 'SELCHANS'  value =           31
AIPS 1: Keyword = 'VLAIFS  '  value = 'A       '

I am still confused by this as there are 31 frequency channels but the
frequency is given for pixel 64.  This in itself might not be a problem
except for the fact if the header information is correct then my line
seems to be in the wrong place ie at a velocity of 1900 km/s rather than
1400 km/s. I could well be being silly though.

Sorry to bother you and thank you very much for your help.

regards
Harriet


On Thu, 10 Jul 2003, Eric Greisen wrote:

> Your initial question refers the the VLA archives and so I expected to
> see a UV data header.  Instead I see a header for a Cleaned image.  It
> is entirely possible that the original data had many spectral channels
> but that the subimage retained was a portion from the earlier part of
> the spectrum.  The reference pixel is corrected in AIPS when subimages
> are taken, but it may well be off the remaining image as a result.
>
> The raw uv-data archives were changed into a format that aips should
> be able to read (unless there were bugs in the translator program -
> and there were a few for abnormal modes).  The image FITS format has
> not changed ("Once FITS always FITS" is a world-wide principle) and
> aips should have no trouble reading images especially those we wrote.
>
> If this does not answer your question, please provide more details on
> where this image header actually came from.
>
> Eric Greisen
>