[daip] Fxpol troubles.. (fwd)

[Chris Flatters]

> I'm starting the reduction of my project ED009 (Nov98, line experiments
> observed with the EVN in dual polarization and correlated at Socorro)
> and I have a problem with the labeling of polarization axes.
> 
> As usual when I download the data, the polarization appears to be two
> separated IFs, normally this is corrected running the task FXPOL.
> 
> Well in my case, after running FXPOL I obtained 1 IF and two
> polarization axes but these axes are label: LL and RL (and not LL and
> RR).  I tried different version of AIPS and the problem persists.  I
> tried to corrected by hand using GETHEAD/PUTHEAD but the CTYPEn are
> all empty.
>  
> How can I correct the label of the second polarization axes?

Your experiment was observed using a polarization scheme that assigned
LL to the odd numbered bands and RR to the even numbered bands. Versions
of FXPOL prior to May 24, 2000 can not deal with this.

The easiest way to procede is to use the 31DEC99 version of AIPS and to
set BANDPOL to '*(LR)'. Ensure that the midnight job has run at least
once since May 24 to make sure that you have an up to date version of
FXPOL.

Your only other course of action is to use UVCOP to copy your 2 IFs
to separate files and then to use VBGLU to combine the 2 in reverse order.
You should then use AXDEFINE to change the reference value for the STOKES
axis from -2 to -1 in the VBGLU file and run FXPOL on this file.

	Chris Flatters
	cflatter at nrao.edu