Monochromatic Atmospheric Extinction Coefficients at La Silla

This page contains information about the atmospheric extinction coefficients. These values have been determined by using the Swiss Telescope, during the photometrics night, using either a two-channel photelectric photometer(P7) or a CCD camera.

The data is given as values of HJD, Date, kU, kB1, kB, kB2, kV1, kV, kG, kR and kI, where the ki values are the mean extinction in each of the 9 filters ( U B1 B B2 V1 V G R I).

The mean wavelengths of the filters (in Angstrom) are:

   U   B1   B    B2    V1    V    G    R   I 
 3464 4015 4227 4476 5395 5488 5807 6760 7610

You can see the data by year and by month:

If you want to see an specific night click here

REMARK: The extinction data will no more delivered to us,now it is available on the Geneva Observatory Webpage


Description of the data reprinted from ESO Messenger No. 80 (June 1995), pages 34, 35, 36. This article may be copied for further use with the indication of the ESO Messenger as source.

These data are property of the Geneva Observatory Photometric Group. They can be used for the reduction of the data obtained by using ESO Telescopes. They cannot be used without agreement in publications on the Atmospheric Extinction itself.

Further La Silla Astroclimatology Data