Astropart.Phys.20:111-128,2003 H.E.S.S. -- the High Energy Stereoscopic System -- is a new system of large
imaging atmospheric Cherenkov telescopes, with about 100 m^2 mirror area for
each of four ...telescopes, and photomultiplier cameras with a large field of view
(5 degr.) and small pixels (0.16 degr.). The dish and reflector are designed to
provide good imaging properties over the full field of view, combined with
mechanical stability. The paper describes the design criteria and
specifications of the system, and the individual components -- dish, mirrors,
and Winston cones -- as well as their characteristics. The optical performance
of the telescope as a whole is the subject of a companion paper.
Mirror facets of the H.E.S.S. imaging atmospheric Cherenkov telescopes are aligned using stars imaged onto the closed lid of the PMT camera, viewed by a CCD camera. The alignment procedure works ...reliably and includes the automatic analysis of CCD images and control of the facet alignment actuators. On-axis, 80% of the reflected light is contained in a circle of less than 1 mrad diameter. The spot widens with increasing angle to the telescope axis. In accordance with simulations, the spot size has roughly doubled at an angle of 1.4 degr. from the axis. The expected variation of spot size with elevation due to deformations of the support structure is visible, but is completely non-critical over the usual working range. Overall, the optical quality of the telescope exceeds the specifications.
H.E.S.S. -- the High Energy Stereoscopic System -- is a new system of large imaging atmospheric Cherenkov telescopes, with about 100 m^2 mirror area for each of four telescopes, and photomultiplier ...cameras with a large field of view (5 degr.) and small pixels (0.16 degr.). The dish and reflector are designed to provide good imaging properties over the full field of view, combined with mechanical stability. The paper describes the design criteria and specifications of the system, and the individual components -- dish, mirrors, and Winston cones -- as well as their characteristics. The optical performance of the telescope as a whole is the subject of a companion paper.
