Posts Tagged ‘telescope mount’

Azimuth

The angle measured from the south point of the horizon toward the west to a point at the foot of a star’s vertical circle. When used as an indication of the position of a star on the imaginary celestial sphere it is referred to as Right Ascension.

Altazimuth Mount

A type of telescope mount, which allows the instrument to be moved freely in declination (altitude) and right ascension (azimuth) hence the name altazimuth mount.

The altazimuth mount is the simplest of all of the telescope mounts. It has two axes that are set at right angles to each another. These two axes permit movement vertically and horizontally, allowing a telescope to be directed at any point in the sky. The big disadvantage is that, unlike an equatorial mount, it requires continual adjustment to counteract the Earth’s rotation in order to keep an object in view. It is for that reason that the altazimuth mount has long been associated with cheap telescopes and beginners telescopes. It is simple and cheap to produce. It was the first effective¬† type of telescope mount and dates back to the 16th century, when telescopes were first invented.

With the advent of computers, that all changed. When drive motors controlled by computers are added to the two axes, it then becomes straightforward to follow an astronomical object.

The 6-meter Bol’shoi Teleskop Azimultal’nyi (BTA), Nizhnii Arkhyz, Russia was commissioned in 1976. It was the first large optical telescope to use an altazimuth mount. It is located on the slopes of Mount Pastukhov on the northern side of the Caucasus Mountains. The telescope uses an f/4 primary mirror giving a 26-meter tube housed in a dome 58m in height.

The computer for the Bol’shoi telescope was a complex mainframe initially but the same digital tracking¬† technology is now available to amateurs on their own computers or built into the telescope control system.¬† Examples of these telescopes can be found from the main manufacturers such as Meade, Celestron and so on. Very little setting up is required, other than the mount is perfectly level to begin with. ‘Teach’ the computer where it is by showing it two known objects and the software will do the rest.

Because of it’s cheap and robust construction, altazimuth mounts are increasingly used for the worlds largest professional telescopes. That keeps costs down and to divert money to more crucial systems.

For amateurs, the Dobsonian mount brought portability to owners of larger Newtonian reflecting telescopes. The Dobsonian mount is a version of the altazimuth mount. It is essentially a box shaped fork with two semicircular recesses ar the top of each fork. The telescope sits in the recesses in the top which permit vertical movement. The base of the fork rests on short vertical axis and a teflon coated flat plate. That permits horizontal movement. It is not uncommon now to have fairly easily portable 30cm or greater Newtonian reflectors.

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