THE OPTICAL LAYOUT OF THE HEGRA CHERENKOV TELESCOPES

The raytracing technique was used to derive a suitable design for the HEGRA system of Cherenkov telescopes, which is at present commissioned at La Palma. The reflectors with a diameter of similar to 3.9 m consi st of 30 spherical mirrors with focal lengths in the range of 4.88 - 4 .94 m. It is shown that 93% of the photons from the Cherenkov light em itted by an extended air shower are contained in the camera pixels, 0. 25 degrees in diameter, for the full field of view of theta = +/- 2.5 degrees. The optical performance of the HEGRA design is compared to ot her layouts.