Converse's Reviews > The Telescope: Its History, Technology, and Future

The Telescope by Geoff Andersen
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's review
May 22, 2011

really liked it
bookshelves: non-fiction, science, astronomy, technology, physics, history
Read from May 21 to 22, 2011

The author, a physicist working at the U. S. Air Force Academy, describes the different ways a telescope can be built (refractors, reflectors, Schmidt-Cassegrians, and so on) and the instruments they use. The author emphasizes that resolution (how far apart two objects need to be for us to tell that there are two, rather than one, thing out there) and light gathering ability limit our ability to detect objects much more than magnification does. Until the last few decades, not much could be done to improve resolution (because atmospheric turbulence was the most important cause of lower resolution), but light gathering could be increased by making larger mirrors. The new technique of making mirrors out of separate segments has allowed for much larger mirrors, a technique made practical by the concurrent development of computers to keep these segments properly aligned. Furthermore, the technique of adaptive optics, in which the shape of the overall mirror is adjusted to keep the image of a guide star or of laser light reflected off of sodium atoms in the out atmosphere, sharp has greatly improved for ground based telescopes. In addition, putting telescopes into orbit also avoids the problem of atmospheric factors reducing resolution. The adaptive optics technqiues were originially developed for spy satellites and were declassified in the early 1990s to the benefit of astronomers. The author mainly discusses astronomical telescopes, but also describes the physics behind spy satellites and lidar. Lidar is a remote sensing technique, analagous to radar, but using laser pulses rather than radio or microwaves. It can be used to make extremely accurate topographical "maps" and can also be used to detect wind shear, a useful thing to know around airports as arriving and departing planes are very vulnerable to sudden severe gusts. As the receiving device for lidar is a telescope, there is a connection to the main topic. In terms of instruments used in conjunction with telescopes, the author describes such imaging techniques as photographic imulsions (mostly out of date now), digital devices like CCD (similar to a digital camera), specrometry, and inferometry. The author keeps the equations to a minimum.

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