Transit instrument
It has been suggested that Transit telescope and Meridian circle be merged into this article or section. (Discuss) Proposed since February 2010. |
In astronomy, transit instruments are used for the precise observation of star positions. The instruments can be divided into three groups:
Contents
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)
Universal instruments
which allow transit measurements in anyone direction
- Astronomical theodolites
- Altaz telescopes with graduated eyepieces (also for satellite transits)
- Cinetheodolites
Zenith instruments and Astrolabes
- Zenith telescope
- Photozenith tube (PZT)
- zenith cameras
- Danjon astrolabe, Zeiss Ni2 astrolabe, Circumzenital
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
- Position astronomy, Astrogeodesy
- latitude/longitude observation, vertical deflection
External links
- 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
- Transit instrument in the Encyclopedia.com
- Transit circle technique (Classic Encyclopedia)
- Great Transit at Lick Observatory, +Photo
- Modern roboter telescopes
- The Carlsberg Automatic Meridian Circle
- Photo of a 19 century Transit Instrument (Jones 1826)
- Transit instruments udes by the Survey of India, 1867)de:Durchgangsinstrument