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A telescope mount is a mechanical structure which supports a telescope. Telescope mounts are designed to support the mass of the telescope and allow for accurate pointing of the instrument. Many sorts of mounts have been developed over the years, with the majority of effort being put into systems that can track the motion of the stars as the Earth rotates with a single motion.
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Alt-az mounts
Main article: Altazimuth mount
The earliest types of mounts are today known as altitude-azimuth, or alt-az systems. The name refers to the way the system allows the telescope to be moved in altitude, up and down, or azimuth, side to side, as separate motions. One limitation of this mount is that the telescope's field-of-view rotates at varying speed as the telescope tracks, whilst the telescope body does not, thus causing problems with astro-photography, for example. This type of mount is used in practically all modern big telescopes, and has also become popular with inexpensive commercial and hobby constructions.
Equatorial mounts
Main article: Equatorial mount
The introduction of the equatorial mount displaced most alt-az systems for many serious users for several centuries. By tilting the horizontal base of an alt-az system up until it is parallel to Earth's equatorial plane, the azimuth rotation then swings the telescope in an arc that follows the stars as they move across the sky due to Earth's rotation. By attaching a simple clockwork mechanism to this axis, the equatorial system makes long observation easy. Also the telescope's field-of-view does not rotate, which all combined make these simpler tools to use in e.g. astro-photography.
Equatorial mounts come in different shape, most common forms include German Equatorial Mount (GEM in short), equatorial fork mount, and equatorial platform.
Transit mounts
Transit mounts are single axis mounts usually orientated so the instrument can pivot (transit) on a north-south axis. This allows the telescope to view the whole sky, but only when the earth's rotation allows the objects to cross through that narrow north-south line (the meridian). This type of mount is used in Transit telescopes, designed for precision astronomical measurement. Transit mounts are also used to save on cost or where the instruments mass makes movement on more than on axis very difficult, such as large radio telescopes.[1]
Fixed mounts
Some telescopes are entirely fixed, such as Zenith telescopes that point only straight up and the National Radio Astronomy Observatory's Green Bank fixed radio 'horn' built to observe Cygnus X-1.
Hexapod-Telescope
Instead of the classical mounting using two axles, the mirror is supported by six extendable struts (hexapod). This configuration allows moving the telescope in all six spatial degrees of freedom and also provides a strong structural integrity.
References
See also
- GoTo (telescopes)
- History of the telescope
List of telescope parts and construction - List of telescope types
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