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Transit instrument

astronomical instrument

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Record originEnglish Wikipedia
Text licenseCC BY-SA 4.0
Source revisionJun 23, 2026
Entity authorityQ6933280 ↗
Source-derived summary

In astronomy, a transit instrument is a small telescope with an extremely precisely graduated mount used for the precise observation of star positions. They were previously widely used in astronomical observatories and naval observatories to measure star positions in order to compile nautical almanacs for use by mariners for celestial navigation, and observe star transits to set extremely accurate clocks (astronomical regulators) which were used to set marine chronometers carried on ships to determine longitude, and as primary time standards before atomic clocks. The instruments can be divided into three groups: meridian, zenith, and universal instruments.

Types

Meridian instruments

For observation of star transits in the exact direction of South or North:

Meridian circles, Mural quadrants etc.

Passage instruments (transportable, also for prime vertical transits)

Zenith instruments

Zenith telescope

Photozenith tube (PZT)

zenith cameras

Danjon astrolabe, Zeiss Ni2 astrolabe, Circumzenital

Universal instruments

Allow transit measurements in any direction

Theodolite (Describing a theodolite as a transit may refer to the ability to turn the telescope a full rotation on the horizontal axis, which provides a convenient way to reverse the direction of view, or to sight the same object with the yoke in opposite directions, which causes some instrumental errors to cancel.)

Altaz telescopes with graduated eyepieces (also for satellite transits)

Cinetheodolites

Observation techniques and accuracy

Depending on the type of instrument, the measurements are carried out

visually and manual time registration (stopwatch, Auge-Ohr-Methode, chronograph)

visually by impersonal micrometer (moving thread with automatic registration)

photographic registration

CCD or other electro optic sensors.

The accuracy reaches from 0.2" (theodolites, small astrolabes) to 0.01" (modern meridian circles, Danjon). Early instruments (like the mural quadrants of Tycho Brahe) had no telescope and were limited to about 0.01°.

See also

Astronomical transit

Latitude/longitude observation, vertical deflection

Positional astronomy, astro-geodesy

References

Further reading

Karl Ramsayer: Geodätische Astronomie, Vol.2a of Handbuch der Vermessungskunde, 900 p., J.B.Metzler, Stuttgart 1969

Cauvenet and Brünnow's Handbooks of Spherical Geodesy

External links

"Transit instrument". The Columbia Encyclopedia (6th ed.). The Columbia University Press.

Editorial summary

This brief starts where responsible research should: with the source description of “Transit instrument” as astronomical instrument. Everything that follows is an evidence route, not borrowed authority.

Editorial reviewA practical starting point whose main value is the path it opens into stronger specialist and primary sources. The current lead gives the account dated anchors—1969—that can be checked directly. The selected authority fields contribute no independent date. The account is most persuasive where Transit, instrument and astronomical can be independently traced.
Editorial analysis

Why this record matters

The subject matters to the general reference register because the source frames it as astronomical instrument. Its deeper value depends on whether names, dates, institutions and citations support that framing.

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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Jun 23, 2026. The linked authority identifier is Q6933280. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1969.

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This entry incorporates text from “Transit instrument” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.