Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A New Mirror Alignment System for the VERITAS Telescopes   Imaging atmospheric Cherenkov telescopes (IACTs) used for ground-based
gamma-ray astronomy at TeV energies use reflectors with areas on the order of
100m$^2$ as their primary optic. These tessellated reflectors comprise hundreds
of mirror facets mounted on a space frame to achieve this large area at a
reasonable cost. To achieve a reflecting surface of sufficient quality one must
precisely orient each facet using a procedure known as alignment. We describe
here an alignment system which uses a digital (CCD) camera placed at the focus
of the optical system, facing the reflector. The camera acquires a series of
images of the reflector while the telescope scans a grid of points centred on
the direction of a bright star. Correctly aligned facets are brightest when the
telescope is pointed directly at the star, while mis-aligned facets are
brightest when the angle between the star and the telescope pointing direction
is twice the misalignment angle of the facet. Data from this scan can be used
to calculate the adjustments required to align each facet. We have constructed
such a system and have tested it on three of the VERITAS IACTs. Using this
system the optical point spread functions of the telescopes have been narrowed
by more than 30%. We present here a description of the system and results from
initial use.

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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-th
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The categories of this paper are: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: cs
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The categories of this paper are: q-bio
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The categories of this paper are: q-alg
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The categories of this paper are: quant-ph
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The categories of this paper are: supr-con
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The categories of this paper are: mtrl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-lat