Star transit

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A Star transit is the passage of a star through the eyepiece of a telescope.

Star transits (Reticle 2°, magnif.~10, two stars passing the vertical thread). Timing accuracy may be ±0,5s

The precise observation of star transits is the basis of many methods in Astronomy and in Geodesy. The measurements can be done in different ways:

  1. visually (mostly up to 1990): accuracy 0,1" to 2" (depending on the instrument); timing with digital clocks about 0,05-0,2 seconds
  2. by CCD and other electro-optical sensors: as above, time often better
  3. semi automatic instruments: Photography or "impersonal micrometer", ca. 2 times better than No.1
  4. by Scanning methods: Astrometry satellites like Hipparcos about 0,01".


See also[edit]