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: http://www.astronomy.net/articles/10/intro.html
Дата изменения: Unknown Дата индексирования: Sun Apr 10 00:32:33 2016 Кодировка: Поисковые слова: stonehenge |
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by
John Huggins
We start our photographic journey in the middle of the instrument located on top of Anderson Mesa, just outside the city of Flagstaff, Arizona.
View of the Instrument's Center
The white buildings house a type of telescope called a siderostat. Each houses a 0.5 meter mirror which collects the starlight and sends it to a mirror system which guides the light to a central building. These units are alt-az mountings. Each axis is driven by a stepper motor through a step down transmission. The whole siderostat assembly rides on top of a three point stand which sits on top of three concrete pillars. These pillars are solid all the way down to the bedrock to provide high stability. The little black ball in the middle of the mirror is a retro reflector for laser beams behind. These lasers form a very precise distance measuring system which keeps track of the mirror's movements with respect to the bedrock. This measurement system can track changes of less than 20 billionths of a meter.
After the starlight hits the siderostat mirrors, additional mirrors guide the light to a feedbeam tube system. Each siderostat sends its beam of light down one tube. Each tube maintains a vacuum to eliminate beam deformations. Shown here are three feedbeam tubes. Eventually, the instrument will have six tubes.
[Beginning] - [Next Page - Starlight Path]
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