Transit instrument

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In astronomy, transit instruments are used for the precise observation of star positions. The instruments can be divided into three groups:

Meridian circle at the Kuffner observatory in Vienna, Austria

Meridian instruments[edit]

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

Universal instruments[edit]

which 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.) (Wolf and Brinker 183–6)
  • Altaz telescopes with graduated eyepieces (also for satellite transits)
  • Cinetheodolites

Zenith instruments and Astrolabes[edit]

Observation techniques and accuracy[edit]

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

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[edit]


  • Wolf, Paul R and Russell C. Brinker. Elementary Surveying, 8th ed. New York: Harper Collins, 1989.

External links[edit]