Vulcan South Equipment
Mount
The Vulcan South photometer is mounted on the Australian-built
Generic Mount, or Gmount. The mount was originally designed
to be used as part of the Automated
Astrophysical Site Testing Observatory (AASTO), a joint
University
of New South Wales (UNW) - Australian
National University (ANU) - Center
for Astrophysical Research in Antarctica (CARA) initiative.
The Gmount was designed to operate on very low power in the
extreme cold of the Antarctic Plateau. Site testing at the
South Pole from the AASTO was completed in 2003, making the
Gmount available for our use.
Photometer
The Vulcan South Photometer is essentially a large precise
light-meter that measures the brightness of thousands of stars
simultaneously. It is called a photometer because it is designed
for precise brightness measurements rather than diffraction-limited
imaging like most telescopes. Our system is a refractor using
a fast lens and CCD camera detector mounted on a temperature
compensated stable optical bench. The optics are enclosed
in an insulated and heated shell and look out through a 10-inch
optical window.
CCD Camera
The photometer consists of a Roper Scientific 500-series
CCD camera with a 4096x4096 pixel Kodak KAF-16800 front illuminated
chip with 9 micron pixels. The camera was supplied by Zoran
Ninkov and is the same one that was previously used for the
Vulcan Camera
Project in 1998-2000 and for our test deployment to the
South Pole in Feb 2001.
Lens
We are using a surplus Aerojet-Delft reconnaissance lens
(S/N 76749). The lens has a 12-inch focal length with an 8-inch
aperture (f/1.5). The lens offers a relatively large light
gathering capability with a short focal length, allowing us
to observe a wide field-of-view while gathering enough photons
to keep the intrinsic (Poisson) noise in our measurements
small. The lens was purchased through ebay and tested extensively
by Zoran Ninkov at the Rochester Institute of Technology and
at the Corning Tropel Corporation. Lens
test results indicate that the lens provides a well focused
image at the red wavelengths where we are observing.
Filters
Our system does not have a filter changer, so we have tried
to optimize the single filter given the constraints of our
project
- maximize
throughput of starlight,
- minimize
background light (especially aurora),
- select
a wavelength where our optics are optimized,
- select
a wavelength where CCD sensitivity is high.
We have selected a filter from Custom
Scientific whose spectral
response was chosen to be as wide as possible while avoiding
the bright oxygen (OI) line at 6300 angstroms and the night
sky lines beyond about 7200 angstroms.
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