[evlatests] collimation results

[Ken Sowinski]

There was a collimation run last night which provided updates
for the newly installed receivers.  Below are the changes
to collimation.
                    Az      El
ea11 at C band   -0.44   +1.79
ea19 at Q band   +0.23   +0.13
Someone will have to make these changes to the oarameter
database.

There were small changes to ea17 and ea21 which I choose
to ignore until they can be confirmed.

The subreflector problem at ea13 remains.  The zero point is now
offset in the other direction and about half as far as it was.
Antenna 13 will not be useful until the subreflector can be
indexed again.  If possible, we should try to determine the
cause of the offset.

va20 is doing strange things, but that is not an evla issue.

I include below my description from last month of the VLA
Q band pointing problem.  It is still there.

On Sat, 22 Sep 2007, Ken Sowinski wrote:

> There was a pointing run last night which was rather boring
> except for the Q band results.  All the VLA antennas, except
> for VA08, provided no solutions; all the trials were rejected
> on the grounds of estimated beam width.  When the threshold
> was increased by about 10 percent solutions were provided
> for all the VLA antennas and all antennas wanted a change
> in azimuth collimation of about +0.25 arc-min.  Collimation
> at all other bands, including K band, were reasonable.  I
> do not believe this result and have not changed any of the
> VLA Q band collimation terms.
>
> All the EVLA antennas, except EA14, were well collimated
> at Q band.  Collimations were updated for EA14 at C and
> Q band.
>
> There has been an earlier collimation run, without Modcomps,
> claiming that all the VLA antennas were fine.
>
> It seems we must have broken something between August 30
> and September 22.  It cannot be subreflector rotation, for
> a small change there would move the beam mostly in elevation.
> Can anyone thing of something we changed which affects
> azimuth pointing, but only at Q band, and onlt for VLA
> antennas?