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Grasslands Observatory: Color Images of Selected Arp Galaxies |
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These tri-color CCD images were obtained at various times
from 1996 to the present. The very earliest were taken with an
HPC-1 camera (1024 x 1024, twelve micron TI chip) or an
Apogee
AP7 camera (512 x 512, 24 micron SITe chip). The HPC-1 was an
excellent early camera with small pixels. The AP7 had a greater photon
efficiency, particularly in the blue portion of the spectrum.
In
March 2001, a
Finger Lakes Instrumentation Dream Machine CCD camera was
installed at the Grasslands Observatory. This camera has a high quantum
efficiency SITe 1024 x 1024 twenty-four micron CCD chip. It
provides a nearly 28 minute field of view on the 24-inch f/5
reflector at the observatory. The Dream Machine is
used in operation with a Finger Lakes Instrumentation CFW-1
Color Filter Wheel and an
Optec TCF
temperature compensating focuser. The filter wheel contains
Photometric R, V, B and I filters and also has an Open slot (O).
This instrument combination is now used for much of the imaging
at the Grasslands Observatory.
Exposures typically range from R = 1 minute, Green (V) = 1.5
minutes, B = 2 minutes, and O = 1-2 minutes to R = 4 minutes,
Green (V) = 6 minutes, B = 8 minutes, and O = 5-20 minutes for
the Dream Machine CCD camera. Short exposures are used for
bright clusters, and long exposures are used for faint galaxies
and nebulae. Most color imaging now is performed using a
Luminance technique with Open or Clear exposures used for the
Luminance (L) part of the color composition.
In late 2007 a Quantum
Scientific Imaging (QSI) 532 CCD was acquired with an LRGB
filter set as well as a hydrogen alpha filter all residing in
the QSI 532 internal color wheel. The QSI 532 CCD has a
Kodak KAF-3200ME 2184 x 1472 chip with 6.8 micron pixels.
This camera can give very high resolution images with the
24-inch telescope, but guiding is critical, and 2x2 binning is
sometimes used for imaging. Typical exposures for black
and white pictures are 5-minute single exposures or three to ten
5-minute exposures median combined. For color imaging, the
black and white exposures are combined with 5 minute or longer
exposures through red, green, and blue, or hydrogen alpha
filters.
tbh 18 April 2010
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Dream Machine CCD Camera combined with a Finger Lakes CFW-1 Color Filter Wheel
All images are oriented with the North at the top and the West
to the right. |
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Table of Arp Galaxies |
Color Images of Selected Arp Galaxies |
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