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Technical implementations » Mirrors

The active reflective mirror surface of each telescope is 236 square meters. MAGIC-I originally consisted of 974 square mirror elements of 49.5x49.5cm diamond-milled aluminium with quartz coating. Four mirror elements (three elements at the some panels at the edges) are mounted and pre-adjusted on a 1x1m panel. The panels have a 13 kW heating system to prevent dew deposition and icing of the mirror surface. Over the years, some elements were replaced by new aluminium or in some cases glass mirrors, and in 2014 around 60 panels were replaced by 99x99cm glass mirrors. In this major mirror exchange some damaged elements were removed and the weight of the dish was reduced by more than 1 ton. MAGIC-II consists of 246 99x99cm mirror panels, the outer part is made up of 104 glass mirrors, the inner part of 142 aluminium panels. The focal length and diameter of the parabolas are both around 17 meter, so the focal length to diameter ration is f/D = 1.03.

The maximum deviation of and individual mirror element from the ideal paraboloid is less than 10 micrometers, the mean roughness is 4 nanometers. The average reflectivity, focussed on a spot of 2 cm radius at wavelengths between 290-650 nm, is around 80%.

Each mirror panel is mounted on three points, one fix point and two computer-controlled actuators that can move the panel in any direction. Automatic adjustment of the mirror panel orientation by an Active Mirror Control system ensures optimum focusing for each telescope pointing.