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Saturday, February 06, 2010

4-m at dewar fill position

Modern telescopes need to have their instruments attended to before most nights - in this case, the dewar that keeps the Mosaic detectors cold to reduce background noise must be filled. Dave the Observing Assistant who runs the telescope all night is at far left on the orange platform and the telescope is pointed low so that he can get at the dewar. The black cylinder is the secondary mirror support for the Cassegrain focus and is also the "Prime Focus" cage. The Mosaic detectors are mounted at Prime focus with the mirror removed from the bottom of the cage. In the old days, the observer would ride inside the prime focus cage all night, guiding on a field star to get one of those spectacular photos you probably remember from your grade school science class. This image was taken with my 10mm fisheye lens with an exposure of 1/15 seconds at f/3.2, ISO 400.
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