Star orbit
A star orbit is the track that a fixed star draws through the field of view of a telescope as a result of the earth's rotation or leaves on the photographic film or the CCD sensor of a camera . Sometimes it is also understood to mean the apparent path of a star relative to the neighboring objects in the starry sky . Star orbits are a special form of orbital lines and are approximately circular in photographic imaging.
Measurements on apparent star orbits
In astronomy and geodesy , such star orbits are measured with precision instruments - depending on the effort and purpose with accuracies of 1 ″ down to 0.01 ″, with astrometric satellites even up to 0.001 ″. These measurements can be made:
- visually on the thread net as a stop of a star passage, or with semi-automatic tracking ( impersonal micrometer )
- with photographic or electronic image processing
- with partially automated special instruments such as a comparator , various measuring microscopes or with scanning methods.
The measurement of apparent star orbits is the basis of many astrometry and astrogeodesy methods - regardless of which of the above methods is used to observe the passages. In space travel , too , analyzes of recorded star trails are sometimes an aid for localization or course correction .
Other uses
The apparent movement of stars also serves other purposes, such as
- in planetariums or at public observatories to demonstrate the rotation of the earth to visitors
- to determine the apparent diameter of planets (the starry sky rotates at approx. 15 ″ per second, so that e.g. Jupiter with an average size of 45 ″ needs exactly 3.0082s / cos δ to cross the crosshairs )
- for determining the magnification or field of view of telescopes
- for estimating instrument errors and wobble of mechanical axes
- for short-term recordings to create an approximate star map
- or simply for appealing pictures - for example of the starry sky as it appears to revolve around the North Star .
See also
- Upper and lower culmination , greatest digression , parallactic angle
- Reflecting telescope , theodolite , angle measurement , accuracy ,
- Photography , star color , apparent location , star position , FK6 , star atlas
- Direction measurement , spatial position , latitude
- Sky clock for approximate determination of the time.
literature
- Klaus Schnädelbach : Simultaneous location determination through photography of the star orbits . Ed .: DGK (= C . Band 99 ). Munich / Karlsruhe 1966.
- Albert Schödlbauer : Geodetic Astronomy - Basics and Concepts . De Gruyter-Verlag, Berlin / New York 2000.
- Gottfried Gerstbach : Eye and sight - the long way to digital recognition . In: Star Messenger . Issue 2000/8. Vienna 2000, p. 160-180 .