please find below a short summary of the activities related to the AO system.
People at LBTO:
Positive environmental conditions allowed telescope activities tonight.
The shell was successfully set at 01:28UT. A preliminary inspection of the gap showed it is on its nominal range of values (24um<pos<39um).
The first part of the night was devoted to measure the AdSec
astigmatism at changing elevation, also to improve the previoulsy calibrated LookUpTable
. 14 points were sampled, with elevations ranging from 20° to 85°. At any position, a command was given to the shell and through IRTC the resulting image was observed. The correction value that resulted in the best image was taken as the astigmatism correction for that elevation. IRTC was operated remotely by J.Hill, who also took care of the inspection of the images. The result in shown in the following plot.
To perform the measurement, the automatic high order offload was disabled: an error was found while re-enabling the automatic correction (forces are increasing instead of decreasing). This issue is under analysis now: please note that the correction worked fine during the previous days.
The second part of the night was devoted to WFS testing. The telescope was moved to NSV6945, an F5V
, B=4.7 star, and images were collected both on the WFS technical viewer and he CCD39. Please find below the report of the W-Team that worked remotely.
The dome was closed at 08:51UT, because of wind speed and increasing cloud coverage.
A magnitude 4.7 star was pointed and the WFS unit was setup using the
parameters found during the alignment in the LBT clean room. Starlight
was immediately found on the pyramid and formed pupil images on the
ccd39 without the need of a star acquisition procedure. As expected,
atmospheric turbulence is prominent on single images. A sequence of 2000
frames (corresponding to 10 seconds of integration at the selected rate
of 200 Hz) at high modulation was acquired and averaged. The averaged
image clearly shows the central obstruction and swing arm shadow. The
features on the pupil borders are caused by the actuators removed from
the control loop in the last several days. Intensity is about 2000
counts/pixel, which is about as expected for this star magnitude and
Another test was attempted to refine the pupil position towards the
correct one for closed loop operation, but it was interrupted by the
onset of clouds.
Below: a screenshot of a single frame showing the turbolence (0.005
sec exposure), and the average of 2000 such frames.
Ciao and happy Easter to everybody
- 05 Apr 2010