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A zenith telescope is a type of
Zenith Sector by John Bird
{{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System Telescope types
A zenith telescope is a type of telescope
A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to obse ...
that is designed to point straight up at or near the zenith. They are used for precision measurement of star positions, to simplify telescope construction, or both.
A classic zenith telescope, also known as a zenith sector employs a strong altazimuth mount, fitted with levelling screws. Extremely sensitive levels are attached and the telescope has an eyepiece fitted with a micrometer Micrometer can mean:
* Micrometer (device), used for accurate measurements by means of a calibrated screw
* American spelling of micrometre
The micrometre ( international spelling as used by the International Bureau of Weights and Measures; ...
. They are used for the measurement of small differences of zenith distance, and used in the determination of astronomic latitude
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north ...
.
Other types of zenith telescopes include the Monument to the Great Fire of London
The Monument to the Great Fire of London, more commonly known simply as the Monument, is a fluted Doric column in London, England, situated near the northern end of London Bridge. Commemorating the Great Fire of London, it stands at the jun ...
, which includes a central shaft meant for use as a zenith telescope. High-precision (and fixed building) zenith telescopes were also used until the early 1980s to track Earth's north pole position e.g. Earth's rotation axis position ( polar motion). Since then radio astronomical quasar measurements ( VLBI) have also measured Earth's rotation axis several orders of magnitude more accurately than optical tracking.
The NASA Orbital Debris Observatory, which used a 3 m diameter aperture liquid mirror, and the Large Zenith Telescope, which uses a 6 m diameter aperture liquid mirror, are both zenith telescopes, as the use of liquid mirror meant that these telescopes could only point straight up.
See also
*List of astronomical instruments
Astronomical instruments include:
*Alidade
*Armillary sphere
*Astrarium
*Astrolabe
*Astronomical clock
*the Antikythera mechanism, an astronomical clock
* Blink comparator
*Bolometer
*the Canterbury Astrolabe Quadrant
*Celatone
*Celestial sphere
* ...
* List of telescope types
The following are lists of devices categorized as types of telescopes or devices associated with telescopes. They are broken into major classifications with many variations due to professional, amateur, and commercial sub-types. Telescopes can be ...
* Zenith camera
A zenith camera is an astrogeodetic telescope used today primarily for the local surveys of Earth's gravity field. Zenith cameras are designed as transportable field instruments for the direct observation of the plumb line (astronomical latitud ...
References
External links
Zenith Sector by John Bird
{{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System Telescope types