star transit
Under a star path is defined as the trace, which attracts a fixed star as a result of Earth's rotation through the field of a telescope or leaves on the photographic film or the CCD sensor of a camera. Sometimes understood as including the apparent orbit of a star relative to the adjacent objects of the night sky. Stellar orbits are a special form of railway lines and approximately circular with photographic illustration.
Measurements of apparent stellar orbits
In astronomy and geodesy such stellar orbits are measured with precision instruments - depending on complexity and purpose with an accuracy of 1 " down to 0.01 ", with astrometry even to 0.001 "These measurements can be made.
- Visually on the reticle as a stopping mechanism of a stellar passage, or with semi automatic tracking ( impersonal micrometer )
- With photographic or electronic image processing
- With partially automated special instruments such as comparator, different measuring microscopes or scanning methods.
The measurement of apparent stellar orbits is the basis of many methods of astrometry and geodesy Astro - regardless of by which of the above methods is observed the passages. Also in the aerospace analyzes of recorded star trails sometimes a tool for locating or course correction.
Other Applications
The apparent motion of stars is also for other purposes, such
- In planetariums or on public observatories in order to demonstrate to visitors the Earth's rotation
- To determine the apparent diameter of the planet ( the starry sky rotates at about 15 " per second, so for example, Jupiter with an average size of 45 " takes exactly 3.0082 s / cos δ to traverse the crosshairs )
- For the determination of magnification or field of telescopes
- For the estimation of instrument error and the tumbling of axes
- For short-term recordings to create an approximate star map
- Or simply for appealing images - from about the starry sky, as he seemingly revolves around the North Star.