As a research institute of the
Astrophysical Observatory (SAO) is headquartered
in Cambridge, MA, where it is joined with the Harvard College Observatory (HCO) to form
the Harvard-Smithsonian Center for
Astrophysics (CfA). More than 300 scientists at the CfA are
engaged in a broad program of research in astronomy, astrophysics,
earth and space sciences, and science education.
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SMA Optical Guidescope
The new optical guidescope consists of a Celestron-90 spotting scope,
with diameter 90mm and focal length 1000mm. The CCD camera is an
Electrim EDC1000N with 7.4 micron square pixels and 8-bit electron
wells. Each pixel subtends 1.526 arcseconds on the sky. In
comparison, at a wavelength of 500nm, the telescope can deliver an
angular resolution (1.22lambda/D) of 1.39 arcseconds. Thus the camera
will undersample the diffraction pattern (in most weather conditions).
The camera is controlled by a diskless PC/104 80486-based computer
running Redhat 6.2 Linux. Commands arrive via Ethernet (RPC) and the
subsequent images acquired are relayed via an NFS-mounted disk. A
small circuit board provides an interface between the CS82C55 port on
the PC/104 computer and the focus motor and encoder package. All
these components are housed in an aluminum tube with an optical flat,
O-rings, and hermetically-sealed connectors. Temperature and relative
humidity sensors are mounted inside the enclosure.