Atmospheric extinction


Atmospheric extinction evaluates the sky transparency. Besides the natural extinction due to the molecules of the atmosphere, other sources of sky transparency degradation are clouds and aerosols.



Atmospheric extinction is a relevant to ground-based astronomy in optical and near-infrared wavelengths since it is associated with the absorption/scattering of incoming photons from astronomical sources by the Earth’s atmosphere.

The traditional method to compute the atmospheric extinction is to calculate the reduction in brightness of a star in V and r’ bands (KV and Kr'). The following figure shows the statistical summary of 20 years of KV measured at the ORM (García-Gil et al, 2010)

The cumulative frequency and the histogram of K<sub>V</sub> at the ORM.

Atmosphere Extinction at the ORM on La Palma: A 20 yr Statistical Database Gathered at the Carlsberg Meridian Telescope

The Observatorio del Roque de los Muchachos (ORM), in the Canary Islands (Spain), was one of the candidates to host the future European Extremely Large Telescope (E-ELT) and is the site of the Gran Telescopio Canarias (GTC), the largest optical infrared facility to date. Sky transparency is a key parameter as it defines the quality of the

García-Gil, A. et al.

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Thirty Years of Atmospheric Extinction from Telescopes of the North Atlantic Canary Archipelago

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Laken, B. A. et al.

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Related documents
Report on the Incidence of African dust intrusions at the Astronomical Observatories of the Canary Islands: characterization and temporal analysis

The report concludes that the Canary Islands observatories (Roque de los Muchachos and Teide; ORM and OT) show an extremely clean air and pristine skies, only partially affected by some dust loaded African air mass intrusions in summer time (July‐September). Long term simulations (1958‐2006) of TSP (Total Suspended Particles) for OT and ORM show that no positive trend has been detected since 1958, in good agreement with the in‐situ observations. No positive trend in the inter‐annual variation of dust‐loaded air masses over the OT and ORM scientific facilities. Model simulations show a lower incidence of African air masses over ORM compared to OT, as it was expected by the geographical location of both observatories.