[daip] UVFIX and MERLIN

[Leonia Kogan]

Dear Eduardo,

UVFIX does not recalculate the antenna positions. 
UVFIX should recalculate U,V,W.
UVFIX calculates the baseline projected at the picture plane of the source 
given at J2000. 
So if the source position is given at B1950 its coordinates are recalculated to J2000. 
If  the source position is given at J2000 its coordinates are recalculated 
to J2000 and the baseline projected to the picture plane of the source.

You have to take care about the coordinate system of the antennas position.

As I remember UVFIX support well only VLBA and VLA coordinate system:

VLBA: Left hand sistem with the origin at the Earth center; X at greenwitch;
Z - north;

VLA: Right hand sistem with the origin at the array center; X at the local 
meridian of the array center; Z-north.

Position of the array center can be given by UVFIXPRM(4-7)

Regards

Leonia

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>From owner-daip at kochab.cv.nrao.edu Wed Nov 29 14:22 MST 2000
From: Eduardo Ros <ros at mpifr-bonn.mpg.de>
Subject: [daip] UVFIX and MERLIN
To: aipsmail at cv3.cv.nrao.edu
Date: Wed, 29 Nov 2000 21:32:10 +0100 (MEZ)
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Dear Sirs,

We were trying to work with MERLIN data using AIPS, and we have
found a problem.  We have to change the coordinates of a MERLIN
archive from B1950.0 to J2000.0.  The task appropriate to do
that (we thought) is UVFIX.  The problem is that we do not know
how UVFIX handles with the UV-data.

We have applied UVFIX either with parameters UVFIXPRM=0,0, or 1,0, 
or even 2,0.  In none of those cases the UV-coverage (say, the 
positions of the UV-points corresponding to the different scans) 
from the UVFIX output is the same than from the input file.  They
are completely different (from each other and from the original
one).

A look to the AN-table shows that the antenna positions have not
been changed by UVFIX.  Then the change has been done directly in 
the (u,v)-data.

We were trying to do all that to combine MERLIN and EVN data sets 
using DBCON.

Could you give us any hint of how to proceed with that?

Regards,

Marc Ribo/Eduardo Ros

ros at mpifr-bonn.mpg.de
mribo at am.ub.es

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_________________________________________________________________________
Dr. Eduardo Ros                  Max-Planck-Institut fuer Radioastronomie 
Tel: +49-228-525-292                                   Auf dem Huegel, 69    
Fax: +49-228-525-229                               D-53121 Bonn - GERMANY
mailto:ros at mpifr-bonn.mpg.de  -   http://www.mpifr-bonn.mpg.de/staff/ros/
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