Main problems

There was one fault that caused more than 2 hours downtime during period 43, but I also included the problems with the new detector controller for ALFOSC as this caused in total more than 2 hours downtime spread over the semester.

• 2011-06-22: Building power: 2hr 25m

  When slewing the telescope the power to the building would be cut. As part of the investigation of some errors in tracking during the daytime (see below) some work was done on the tachometer of the telescope azimuth motor which caused the relation between the signal (voltage) that is send by the Telescope Control System (TCS) and the resulting speed to change. This let the telescope to move too fast for the building to keep pace, resulting in building crashes. The relation was adjusted to the correct range.

• 2011-07-06 (onward): ALFOSC CCD controller: 2hr 50m

  Many day- and nighttime tests were made with the new detector controller for the ALFOSC CCD and the corresponding new data acquisition software which resulted in several tweaks and corrections. Still, some errors occurred that caused problems during observing after the initial testing phase. Beyond a few minor bugs that did not cause any downtime and are being corrected in updates of the software, there were two main problems that persisted.

  The most serious problem was the apparent sudden loss of the charge-transfer-efficiency of the CCD in the serial (X-) direction. This required every time a shutting down of the observing system and a reset of the CCD controller to correct which takes a short but significant amount of time. In the end this was found to be a problem in the controller when using a binning factor larger than 4 in the serial direction (which is beyond the specifications). The software and the scripts have been modified to avoid using such a high binning factors.

  A second recurring problem are timeouts of commands given to the detector controller. This general requires a shutting down and restarting of the observing system. This problem is thought to be specific for the ALFOSC/NOT installation as this has never been seen before and cannot be reproduced outside the NOT environment. It is being investigated if this is caused by the (old) networking libraries on the computer being used, and a change in the setup of the computer network involved is planned.