Speaker
Sebastian Mueller
(ETH Zuerich)
Description
Imaging Air Cherenkov Telescopes, including the First G-APD Cherenkov Telescope (FACT), use
segmented reflectors. These offer large and fast apertures for little resources.
However, one challenge of segmented reflectors is the alignment of the single mirrors to gain a
sharp image. For Cherenkov telescopes, high spatial and temporal resolution is crucial to
reconstruct air shower events induced by cosmic rays. Therefore one has to align the individual
mirror positions and orientations precisely. Alignment is difficult due to the large number of degrees
of freedom and because most techniques involve a star. Most current methods are limited, because
they have to be done during good weather nights which overlaps with observation time.
In this contribution, we will present the mirror alignment of FACT, done using two methods.
Firstly, we show a new method which we call Bokeh alignment. This method is simple, cheap and
can even be done during daytime.
Secondly, we demonstrate an enhancement of the SCCAN method by F. Arqueros et al., and first implemented by the McGill VERITAS group. Using a second camera, our enhanced SCCAN is optimized for changing weather, changing zenith distance, and changing reference stars.
Developed off site in the lab on a 1/10th scale model of FACT, both our alignment methods resulted in a highly telescope independent procedure, e.g. both our methods run without communication to the telescope's drive.
We compare alignment results by using the point spread function of star images, ray tracing simulations, and overall muon rates before and after the alignment.
| Registration number following "ICRC2015-I/" | 184 |
|---|---|
| Collaboration | FACT |
Primary author
Sebastian Mueller
(ETH Zuerich)
