October 20th

The retroreflecting optics has been installed by the LBTO crew in the morning around 2:00PM. The dome has been closed all the time due to bad weather conditions.

1) AO system calibration and performance

The measurements of the 4 reconstructors at BIN1,2,3,4 have been done. The calibration data required to go on sky is so completed. The performance of the 4 reconstructors in terms of SR has been found consistent with results given by numerical simulations.

2) AO system

- The procedure to automatically adjust the system overall gain has been completed. The procedure uses the amoeba algorith and on sky measurement to find the optimal gain. Test has been done a bin1 and high flux. The results show that the procedure converges quite close to the gain estimated by the operator. Other test are ongoing.
- The possibility to work with the RR when the telescope is not pointed a Zenith has been tested succcesfully. The system has been used in closed loop up to an elevation of 26 degree.

3) test of M2 astigmatism introduced with elevation.

The AO system has been set in closed loop and the telescope elevation angle has been changed from 90 to 26 degree. The average mirror position in closed loop has been measured every 1 degrees. The mirror position clearly show an astigmantism in the commmands. The astigmatism is encreasing when the elevation angle decreases. The astigmatic term is found to sufffer from hysteresis. In other word the amount of astigmatism is changing when the elevation engle is going back from 26 to 90 degrees. A measurement of the astigmatism behaviour will be repeated tonight. Data reduction is ongoing. Se attached plot for the actual data.

The retroreflector has been kept installed because of the bad weather conditions at LBTO.
  • astigVSelev.png:
Topic revision: r1 - 29 Oct 2010, AlfioPuglisi
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