From:	Marc Balcells 
Sent:	martes, 11 de marzo de 2014 13:34
Subject:	[INGNEWS] WHT oscillations problem solved



Over the years, oscillations in azimuth and elevation have occasionally
been seen at the WHT, but these have been rare and short-lived, and have
had little impact on observing.  In December 2013 oscillations in azimuth 
suddenly began to occur more frequently.  By early 2014, ~ 3% of the 
observing time at the WHT was being lost due to oscillations.  This was
a source of considerable frustration for affected observers.

Tracing the origin of the oscillations, which could not be reproduced during 
the day, proved surprisingly difficult, and required a thorough review of the
mechanical, electronics and software components involved.

A breakthrough came on 25 February when an ING electronics engineer
identified a failing capacitor in the azimuth power amplifier. After replacing 
the degraded capacitor, the azimuth oscillations have not been seen again.

ING continues to monitor closely the tracking performance of the WHT, but we 
are reasonably confident that the oscillations problem has been solved.

We would like to thank observers for their patience when faced with the loss of 
telescope time.

For their role in resolving this stubborn problem, we congratulate the
staff of ING's telescope and instrument group, the staff of the ING operations 
team, and Martin Fisher (ex-ING), who helped our team analyse the diagnostic data.

Marc Balcells
Director ING

Dr. Marc Balcells, Director
Isaac Newton Group of Telescopes
38700 Santa Cruz de La Palma, Canary Islands, Spain
Tel. +34 922 425 403
balcells 'at'