The atmospheric extinction is an important parameter for an astronomical site. The extinction directly affects
the observations reducing the available radiation, but the most relevant effect on the quality of the astronomical
data is the variation of the extinction across the sky and in the course of the observation at night. The aim is
to trace the atmospheric transparency at any astronomical site using MASS data.
The main goal of the present work is estimating the atmospheric extinction coefficient (mag/airmass) from
MASS database. Multi Aperture Scintillation Sensor called MASS is an instrument to measure the vertical
distribution of turbulence in terrestrial atmosphere by analyzing the scintillation of bright stars. Here we are
briefly reminding you of the principles of a MASS instrument and presenting also the detailed description of the
output data. In order to gain better understanding of the atmospheric photometry, we compute the atmospheric
extinction coefficient, its rms, and the associated information from MASS database using the evolution of flux
values of a star measured at ground level versus air mass which accounts for the flux loss. The technique used is
based on the Bouguer low. To treat the statistics data correctly and compute the correct extinction, one has
to know the filter. Correct value of the extinction is critical at most. For this reason, the atmospheric extinction
must be extracted only by good measurements. We then used the quality control of MASS data.
Also, in the current paper, we focus on the evaluation of nocturnal atmospheric extinction coefficient
(mag/airmass) and others statistics (time of acquisition, accumulation time, air mass, and HR number is used as
a star name only for information . . .) at Paranal observatory (70°24’05” W, 24°37’24” S, altitude 2635 m a.s.l,
in Chile.). In addition, the rms error of the coefficient has been calculated. It is absolutely needed to evaluate
the accuracy of each extinction measurement. For the first time, they were obtained from MASS database photo metric processing during 885 nights in the years 2004, 2005, 2006 and 2007. These results will almost lead to
complete its characterization. The project is implemented in the frame of the European Southern Observatory
contract No. PO 014190/HNEU.
We present a characterization of meteorological parameters: Wind and direction speed, temperature, relative
humidity and pressure. Data set is provided by the system of NCEP/NCAR Re-analysis. The statistical
treatment of data will cover the years between 2003 and 2006 for the Observatory Oukaïmeden. An analysis of
monthly, seasonal, and annual results is presented. We calculated the Richardson number for each month of the
year. In addition, this paper describes a comparison between balloon-sounding made at different stations and
coincident model-based meteorological analysis. The comparison allows the assessment reliability of the analysis
in studied period.
KEYWORDS: Refractive index, Astronomy, Coherence (optics), Wavefronts, Spatial coherence, Optical turbulence, Stereolithography, Global system for mobile communications, Atmospheric optics, Temperature metrology
Here we analyse 168 optical turbulence profiles made at nine different locations worldwide by means of free flight balloons equipped with instrumentation. Optical turbulence outer scales Lo, as well as coherence outer scales ℓo are
derived for the different locations and taking into account the contribution of the surface layer [0, 50m], the boundary layer [0, 1km] and the free atmosphere [1km, 30km]. Noticeable changes are found between the different locations, mainly due to the boundary layer contribution. The free atmosphere contribution seems almost the same for each site. There is a very good coherence between the outer scale derived by us and that measured using the Generalized Seeing Monitor (GSM) technique.
The ESO OWL site survey plan includes the analysis of the astronomical
quality of the Atlas mountains in Morocco. In this paper we are presenting the first long time measurement of optical turbulence at Oukaimeden site. For this work we built an instrument called ADIMM for an Automated Differencial Image Motion Monitor, and we use it to the measure the optical turbulence at the Oukaimeden Site. We are describing the instrument and reporting the first results obtained after six month of working on this project. The results of night-time seeing measurements carried out during the period from Jun 14 up to October 01 2003 are presented. The median and mean values of the seeing for the entire period of observations are respectively 0.75" and 0.84".
This work was organized in the framework of contract Num.69651/ODG/02/9005/GWI between the European Southern Observatory (ESO) and Astrophysics and Physics of High Energy Laboratory of the Faculty of Sciences, Cadi Ayyad University (LPHEA).