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Proceedings Paper

On-sky performance of the tip-tilt correction system for GLAS using an EMCCD camera
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Paper Abstract

Adaptive optics systems based on laser guide stars still need a natural guide star (NGS) to correct for the image motion caused by the atmosphere and by imperfect telescope tracking. The ability to properly compensate for this motion using a faint NGS is critical to achieve large sky coverage. For the laser guide system (GLAS) on the 4.2 m William Herschel Telescope we designed and tested in the laboratory and on-sky a tip-tilt correction system based on a PC running Linux and an EMCCD technology camera. The control software allows selection of different centroiding algorithms and loop control methods as well as the control parameters. Parameter analysis has been performed using tip-tilt only correction before the laser commissioning and the selected sets of parameters were then used during commissioning of the laser guide star system. We have established the SNR of the guide star as a function of magnitude, depending on the image sampling frequency and on the dichroic used in the optical system; achieving a measurable improvement using full AO correction with NGSes down to magnitude range R=16.5 to R=18. A minimum SNR of about 10 was established to be necessary for a useful correction. The system was used to produce 0.16 arcsecond images in H band using bright NGS and laser correction during GLAS commissioning runs.

Paper Details

Date Published: 14 July 2008
PDF: 11 pages
Proc. SPIE 7015, Adaptive Optics Systems, 70154B (14 July 2008); doi: 10.1117/12.787974
Show Author Affiliations
Jure Skvarč, Isaac Newton Group of Telescopes (Spain)
Simon Tulloch, Isaac Newton Group of Telescopes (Spain)

Published in SPIE Proceedings Vol. 7015:
Adaptive Optics Systems
Norbert Hubin; Claire E. Max; Peter L. Wizinowich, Editor(s)

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