[evlatests] Image Rotation by 180 degrees confirmed

[Eric Greisen]

Rick Perley wrote:
>     Michael observed Cygnus A on Saturday night with both WIDAR and the 
> VLA, using exactly the same file.   He placed the phase center near the 
> middle of one lobe, so as to more easily determine if we have a problem 
> with our phase conventions, as some earlier observations have suggested. 
> 
>     I have made images of the 6cm data from both the VLA and WIDAR 
> correlator data.  The two databases were calibrated in identical 
> manners.  There is no question whatever that the WIDAR image is rotated 
> by 180 degrees about the phase tracking center.  So (in effect) the 
> WIDAR baselines 'point' the wrong way. 
> 
>    
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Can some test with polarization be done?

there are 2 possible scenarios here:

1. the phase convention is backwards.

2. the order of the 2 antennas is reversed - which would swap not only 
the phase sign but also RL and LR

before a fix is implemented it wouold be good to anser this question.

Eric Greisen