A&A Supplement series, Vol 121, March 1997, 569-573
Received April 1; accepted June 20, 1996
R. Ragazzoni, E. Marchetti, - G. Brusa
Send offprint request: R. Ragazzoni
Astronomical Observatory of Padova, vicolo dell'Osservatorio 5, I-35122 Padova, Italy
CISAS, vicolo dell'Osservatorio 5, I-35122 Padova, Italy
Center for Astronomical Adaptive Optics, 933 N Cherry Ave. Tucson, U.S.A.
Due to the finite height of the mesospheric sodium laser guide star, it is shown that the measurement of absolute tilt done with the multi-colour laser star technique is affected by an uncertainty depending upon the distribution. Two case studies for D=3.58 and D=8.00 meter telescopes are given.
keywords: atmospheric effects -- techniques: miscellaneous -- telescopes