North polar sequence
{{Short description | A sequence of stars defining stellar magnitudes and colors}}
The North polar sequence is a group of 96 stars that was used to define stellar magnitudes and colors.{{cite web|url=http://www.oxfordreference.com/view/10.1093/oi/authority.20110803100239512|title=North Polar Sequence - Oxford Reference|publisher=}} The cluster of stars lies within two degrees of the Northern Celestial pole. That fact makes them visible to everyone in the northern hemisphere.{{cite web|url=http://www.glyphweb.com/esky/concepts/northpolarsequence.html|title=eSky: North Polar Sequence|website=www.glyphweb.com}}
Originally proposed by Edward Charles Pickering, the system was used between 1900 and 1950. Today it has been replaced by the UBV photometric system.
See also
References
Further reading
- {{cite book|author=C.R. Kitchin|title=Astrophysical Techniques, Fourth Edition|url=https://books.google.com/books?id=tZpQR_nYKeYC&pg=PA446|year=2003|publisher=Taylor & Francis|isbn=978-1-4200-5702-7|page=446}}
External links
- [https://web.archive.org/web/20090412074513/http://www.jjdash.demon.co.uk/north-polar-sequence.html Schematic images]
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