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A calibration system is provided consisting of an integrating sphere into which light is fed directly from two hollow cathode lamps (Cu-Ar and Cu-Ne) and a Tungsten lamp for a red continuum source. Light from a further 6 lamps (Fe-Ar, Fe-Ne, Th-Ar, Al/Ca/Mg-Ne, Na/K-Ne and Deuterium) is imaged via fused silica lenses onto 3 mm diameter fused silica light guides. The Al/Ca/Mg-Ne and Na/K-Ne multi-alkali lamps are primarily for use with TAURUS-2, whilst the Deuterium lamp provides a blue continuum source. Any combination of lamps may be used simultaneously. The exit pupil of the integrating sphere is fitted with an obscuring disk to simulate the telescope entrance aperture obscuration, i.e. the secondary mirror structure. The reverse side of the acquisition mirror is used to feed the calibration light to the instrument. Line maps of the Cu-Ar, Cu-Ne and Th-Ar lamps are published in ING Technical Note 84, by J.E. Sinclair.
Two eight-position filter wheels are provided for the comparison system. The filters available in filter wheel A are a clear position, ND filters of 0.2, 0.6, 0.8, 1.8, 3.0 and colour filters GG375 and GG495. The filters available in filter wheel B are a clear position, ND filters of 0.3, 0.5, 0.9, 1.2, 2.0, a BG24 colour filter and a clear position.