Abstract
The Cherenkov Telescope Array (CTA) is
a groundbased observatory for gamma rays with
very high energy characteristics within the range
of 10 GeV to 100 TeV. It is currently still under
development. As the title of the project suggests,
it takes advantage of the Cherenkov radiation that
is produced by the gamma ray’s interaction with
the earth’s upper atmosphere, similar to the
guiding physical principles of VERITAS. The
primary differences are that CTA will feature
more telescopes and possess a larger energy range.
Cherenkov radiation will be collected by
an array of dozens of optical telescopes of various
sizes. These optical telescopes will be composed
of hexagonal mirrors that must be aligned relative
to each other so as to represent the shape of the
telescope as a whole properly. It was in this area
of research that my efforts were focused. The
most recent proposed system with which to align
the mirrors consists primarily of a laser and a
webcam. Sixty to three hundred snapshots are
taken of the laser and the position of the laser’s
centroid in each frame is measured and analyzed
by a custom-written computer program executed
via ROOT. One to ten microns was the ideal
resolution that was required of the system to meet
the needs of this project.
Since the position of the laser’s centroid
was given by pixel number, it was necessary to
determine the ratio of pixels to millimeters via
another ROOT program described in more detail
on the following pages. It was also necessary to
ensure by using an OPENCV analysis program
that the pixels were not saturated. As will be
shown, the consequences of saturation are
bothersome edge effects that produce erroneous
results.