Bibcode
Munoz-Tunon, C.; Vernin, J.; Varela, A. M.
Referencia bibliográfica
A & A Supplement series, Vol. 125, October 1997, 183-193.
Fecha de publicación:
10
1997
Número de citas
74
Número de citas referidas
55
Descripción
Nine months' seeing statistics at the Observatorio del Roque de los
Muchachos (ORM) are presented. Measurements were taken with a
differential image motion monitor on top of a 5-m high tower. From the
whole campaign the mean seeing is 0.76", the median value is 0.64" and
7% of the time the seeing is better than 0.3". The best seeing measured
is 0.17". A seasonal variation is noticeable, better seeing conditions
appearing during summer, which corresponds to the occurrence of a
well-defined inversion layer due to the high prevalence of trade winds.
During the summer, 50% of the time seeing is better than 0.54", value
which drops to 0.46" during June, with a narrow distribution (rms =
0.17"). These figures place the ORM among, or better than, the best
astronomical sites (Paranal and La Silla, Chile) where seeing statistics
are available. When inspecting individual nights, it sporadically
happens that seeing deteriorates abruptly and slowly recovers, with a
1.2-hour exponential decay time. This phenomenon is interpreted in terms
of meteorological instabilities (gravity waves) which trigger a
turbulent regime.