Hamburg 2016 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 80: Gammaastronomie IV
T 80.5: Vortrag
Mittwoch, 2. März 2016, 17:50–18:05, VMP9 SR 27
FACT -- Bokeh Alignment for Cherenkov Telescopes — •Sebastian Achim Mueller1 and Jens Buss2 — 1ETH Zurich, Switzerland — 2TU Dortmund
Imaging Atmospheric Cherenkov Telescopes (IACTs) need fast and large imaging optics to map the faint Cherenkov light emitted in cosmic ray air showers onto their image sensors. Segmented reflectors are inexpensive, lightweight and offer good image quality. However, alignment of the mirror facets remains a challenge. A good alignment is crucial in IACT observations to separate gamma rays from hadronic cosmic rays. We present a simple, yet extendable method, to align segmented reflectors using their Bokeh. Bokeh alignment does not need a star or good weather nights but can be done anytime, even during the day. Bokeh alignment optimizes the facet orientations by comparing the segmented reflector's Bokeh to a predefined template. The Bokeh is observed using the out of focus image of a nearby point like light source in a distance of about ten times the focal lengths. We introduce Bokeh alignment on segmented reflectors and present its use on the First Geiger-mode Avalanche Cherenkov Telescope (FACT) on Canary Island La Palma, as well as on the Cherenkov Telescope Array (CTA) Medium Size Telescope (MST) prototype in Berlin Adlershof.