Night report 2025-08-12

Night report 2025/08/12

Observers: Joyce Naomi Dominique van Dalen  and  Daniele Bjørn Malesani.

Support:  Antonio Martin-Carrillo, Gregory Corcoran, Laura Cotter, Morgan Fraser.

TAT: Giuliano Pignata, Amar Aryan, Michel Dennefeld.

Start (22:50 UT): humidity 17.0%, temperature 15.8 ºC, wind speed 6.1 m/s, 1.1'', airmass 1.23.

Middle (05:05 UT): humidity 12.0%, temperature 15.7 ºC, wind speed 8.3m/s, seeing 1.0'', airmass 1.18.

End (09:59UT): humidity 10.0%, temperature 15.0 ºC, wind speed 4.0 m/s, seeing 1.2'', airmass 1.4. 

Comments: during daytime, adjustments had been made to the ULTRACAM instrument after which the weights on the M4 mirror were not put back, which resulted in the rotator of the telescope not functioning properly. Extra tests needed to be carried out, after which it was decided that we continue observations without the M4 weights since there was no technician available immediately to resolve the issue and the effect is small - Due to the weight distribution being off, the rotator could in principle not move smoothly at some positions which would cause the psf of point sources to be slightly elongated in those specific positions. There were scattered clouds during the middle of the night, but guiding was maintained and observations were not affected. 

Calibrations: bias and arcs taken during evening and morning. An extra GR16 free filter standard star was taken to calibrate PESSTO data from earlier this year upon request.