Building

The 12 temperature sensors (with 0.01 degree accuracy/precision) were re-installed in and around the spectrograph. These are necessary to relate any Echellogram shift to physical phenomena on the spectrograph table, and for further tuning of the temperature stability. These sensors are now part of the general data base of the thermal monitoring system (TMS).

The area in front of the main door and the roof-stones were painted white to attempt to increase the FIES-room temperature stability. For the same reason, a metal screen was installed on the west wall to reduce the effect of heating by the sun. Also, a new (bigger) ventilation fan was installed in the front room. However, during warm days the temperature inside the building still goes above the reference value. Solutions are either to increase the temperature which we try to maintain, or add active cooling. Both these solutions have there disadvantages. It was also suggested to use a different reference temperature in summer. This is not the preferred solution, but maybe it is the 'easy' thing to do.

An other issue with the temperature in the FIES room are the oscillations introduced by the temperature control loops, and it is clear that the on/off control loops need the be replaced by proportional loop electronics. This should both remove oscillations and make excursions around the reference temperature smaller.