H. E. Smith | Winter 2007 |
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Physics 7 - Lecture Summary #4 Astronomical Telescopes |
The sensitivity of the telescope is determined by the collecting area of the objective lens (or primary mirror) which is proportional to the square of the diameter of the primary lens or mirror.
The Great Refractor of Lick Observatory in Northern California was completed in 1888 funded by a bequest from entrepreneur James Lick, who is buried in the telescope mount. The objective lens (at the top of the photograph) has a diameter of 36 inches; the lens has a focal length of 57 feet, bringing light to a focus at the bottom of the telescope where the human is standing. The objective is actually composed of two lenses made of Crown glass and Flint glass which have different refracting properties in order to correct partially for chromatic aberration. For a brief period the Great Refractor was the World's largest optical research telescope. The telescope is no longer used for research, but there is a Summer Visitors' Program which allows public visitors to observe through the telescope and hear a popular lecture. Lick Observatory is operated by the University of California for all Faculty, Research Staff and Students in UC, including UCSD astronomers. |
![]() The Great Refractor of Lick Observatory |
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The lecture continues with Reflecting Telescopes.
Reflecting Telescopes
Basic Forces & Light
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