[daip] Aips Question

[Eric Greisen]

Danielle Lucero wrote:
> Hi Eric,
> 
> As you know I have been working on combining some recent EVLA data with 
> some WSRT data.  I have managed to process the data sets such that when 
> I image them the velocity range, center velocity, and channel width are 
> correct.  The emission in both data sets appears in the same channels.  
> However, I have the problem that the headers look different.  The two 
> image headers are pasted below.  I am not sure how to change the 
> specific header values.  Not sure which values correspond with which 
> ctype and crval and cdelts, etc to use. 
> 
> Danielle
> 
> 
> AIPS 1: Image=ugc09519  (UV)         Filename=UGC9519WSRT .UVSRT .   2
> AIPS 1: Telescope=WSRT               Receiver=WSRT
> AIPS 1: Observer=ProcessD            User #=   22
> AIPS 1: Observ. date=13-JUL-2008     Map date=10-FEB-2013
> AIPS 1: # visibilities     52997     Sort order  TB
> AIPS 1: Rand axes: UU-L  VV-L  WW-L  BASELINE  TIME1
> 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       2  -5.0000000E+00       1.00 -1.0000000E+00    
> 0.00    <------- (this is -5 while the other data set has -1 not sure 
> what this means)
> AIPS 1: FREQ        85   1.4223603E+09     149.65  9.4209562E+04    
> 0.00    <------- (still has a reference with respect to pixel 149)
> AIPS 1: RA           1    14 46 21.102       1.00       3600.000    0.00
> AIPS 1: DEC          1    34 22 14.502       1.00       3600.000    0.00
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: Coordinate equinox 2000.00
> AIPS 1: Rest freq   1420.406         Vel type: OPTICAL wrt SUN
> AIPS 1: Alt ref. value -4.27695E+05  wrt pixel  149.65
> AIPS 1: Maximum version number of extension files of type HI is   1
> AIPS 1: Maximum version number of extension files of type FO 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 FQ is   1
> AIPS 1: Maximum version number of extension files of type NX is   1
> 
> 
> -----
> AIPS 1: Image=UGC9519   (UV)         Filename=U9519       .SPECR .   1
> AIPS 1: Telescope=EVLA               Receiver=EVLA
> AIPS 1: Observer=Katherin            User #=   22
> AIPS 1: Observ. date=25-JUL-2012     Map date=24-AUG-2012
> AIPS 1: # visibilities   5464880     Sort order
> AIPS 1: Rand axes: UU-L-SIN  VV-L-SIN  WW-L-SIN  TIME1  BASELINE
> AIPS 1:            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       2  -1.0000000E+00       1.00 -1.0000000E+00    0.00
> AIPS 1: FREQ        85   1.4085875E+09       1.00  9.4117648E+04    0.00
> AIPS 1: IF           1   1.0000000E+00       1.00  1.0000000E+00    
> 0.00            <----- (entry missing in the other data set)
> AIPS 1: RA           1    14 46 21.127       1.00       3600.000    0.00
> AIPS 1: DEC          1    34 22 14.340       1.00       3600.000    0.00
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: Coordinate equinox 2000.00
> AIPS 1: Rest freq   1420.406         Vel type: OPTICAL wrt SUN
> AIPS 1: Alt ref. value  1.69200E+06  wrt pixel   43.50
> AIPS 1: Maximum version number of extension files of type NX is   1
> AIPS 1: Maximum version number of extension files of type FO is   1
> AIPS 1: Maximum version number of extension files of type FQ 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 WX is   1
> AIPS 1: Maximum version number of extension files of type HI is   1

You will probably need to do several things before DBCON will be happy:

1. Axis 2 Stokes:  WSRT is linearly polarized so -5 means XX and -6 YY.
    You will need to lie here and change the WSRT header:
     keyword='crval2'; keyv=-1,0; puth

2. axis 3 Freq: You should change the WSRT header to make the reference 
freq be at channel 1.
    keyw='crval3'; getn E; geth; getn W; puth
    keyw='crpix3'; getn E; geth; getn W; puth

3. IF axis: the verb axdefine will let you add an axis to the data set 
header of the WSRT and it should not matter if the one is RA,DEC,IF and 
the other IF,RA,DEC since they are all 1 point axes.

The getn E has E = catalog number for the EVLA data and W the catalog 
number for the WSRT data set.

Good luck.

Eric Greisen