Deep sky

Under the term deep sky (literally: "deep sky") those optically observable celestial objects are summarized in amateur astronomy that are outside the solar system (i.e. no asteroids, planets or comets), but are not individual stars. They include all star clusters , nebulae and galaxies .

The term deep sky is not based on any classification of objects in terms of their absolute distance. In fact, deep sky objects can be relatively close, like the Pleiades (M45 in the Messier catalog ): 430 light years ; or very far away, like the Whirlpool Galaxy (M51): about 35 million light years.

observation

The visual and photographic observation of deep sky objects is very popular with amateur astronomers . Some of these objects can be seen with the naked eye. A galaxy visible to the naked eye is the Andromeda Nebula (M31), an open star cluster, for example the Pleiades (M45). An example of a nebula that is visible to the naked eye is the Orion Nebula (M42); the globular cluster Messier 22 is visible to the naked eye as a star-like object .

For visual observation of deep-sky objects, optical devices with a high light-gathering capacity, i.e. large openings, are recommended. Small magnifications are usually advantageous for observation in order to allow as much light as possible to enter the eye. You can of course increase the magnification for detailed observation.

Many deep sky objects can be observed very well with simple optical aids such as binoculars . For detailed observation, amateur astronomers prefer mirror telescopes to normal, mostly faint lens telescopes .

History & Cataloging

• Some deep-sky objects were already known in antiquity and before and were listed in corresponding catalogs. However, some also have the Bayer (from 1603) or Flamsteed (1712) names that are only typical for stars , as they were previously misinterpreted as fixed stars .

• When the systematic search for comets began in the 18th century , it became necessary to distinguish the remaining nebulous celestial phenomena from the comets. The French astronomer Charles Messier described the position of 110 of these objects in his catalog ( Messier catalog ) until 1784 , which became the most famous collection of deep-sky objects.

• Since then, more and more such objects have surfaced. And so John Dreyer wrote the famous New General Catalog in 1888 , which contains almost 8,000 objects.

• Other important surveys were the Hubble Deep Field 1995, Hubble Deep Field South 1998 and the Hubble Ultra Deep Field 2004, which recorded the most distant astronomical object in the range of visible light to date.

Deep sky objects

• Star clusters
  • Open star clusters
  • Globular clusters
• fog
  • Emission nebula
  • Reflection fog
  • Dark fog
  • Planetary nebula
• Galaxies

See also

• List of proper names of deep sky objects

literature

• Erich Karkoschka : Atlas for sky observers. The star atlas for the sky year. With 50 star maps of the entire sky. 2nd Edition. Franckh, Stuttgart 1989, ISBN 3-440-05867-0 .
• Thomas Jäger, Wolfgang Steinicke, Hans-Jürgen Wulfrath: Introduction to visual deep-sky observation. VdS specialist group "Visual Deep Sky Observation", Umkirch 2001.
• Wolfgang Steinicke (Ed.): Practical Handbook Deep Sky. Observation of stars, nebulae and galaxies. Kosmos, Stuttgart 2004, ISBN 3-440-09779-X .

Web links

• Section "Visual Deep Sky Observation" of the Vereinigung der Sternfreunde eV (VdS)
• www.schweifstern.de - amateur photos of deep sky objects and comets
• Complete NGC and Messier database with observation reports (German)
• Deepsky database Searches and filters deepsky objects that are observable even for beginners