There were no faults causing more than 2 hours downtime during period 39, but there was one problem that caused small amounts of down time on various occasions. Although also in total it did not cause 2 hours downtime, it was the single problem that cause the most downtime in the semester so I will discuss it here.
On several occasion there were reports of the telescope making noise and vibrating where a restart of the telescope was needed to solve the problem. Various test and changes were made, none of which provided a clear solution. A return to the old alt/az amplifiers and both altitude tachometers seems to solve the problem. It is believed that by changing any component in the alt/az servo (i.e. amplifiers, PI board, tachos etc) causes it to occasionally go unstable resulting in the reported noised and vibrations. This does imply that a proper tuning of the system is required when replacing any of the components by a different type.
Thomas Augusteijn 2010-02-09