Editing Constellation (section)

===88 modern constellations===
{{Main|IAU designated constellations}}

A list of 88 constellations was produced for the IAU in 1922.<ref name="auto" /> It is roughly based on the traditional Greek constellations listed by Ptolemy in his ''Almagest'' in the 2nd century and [[Aratus]]' work ''Phenomena'', with early modern modifications and additions (most importantly introducing constellations covering the parts of the southern sky unknown to Ptolemy) by Petrus Plancius (1592, 1597/98 and 1613), [[Johannes Hevelius]] (1690) and Nicolas Louis de Lacaille (1763),<ref name="iau-const">{{cite web |title=The Constellations |url=https://www.iau.org/public/themes/constellations/ |publisher=IAU – [[International Astronomical Union]] |access-date=29 August 2015}}</ref><ref>{{cite web |url=http://www.ianridpath.com/constellations1.html |title=Constellation names, abbreviations and sizes |author=Ian Ridpath |access-date= 30 August 2015}}</ref><ref>{{cite web |url=http://www.ianridpath.com/startales/almagest.html |title=Star Tales – The Almagest |author=Ian Ridpath |access-date=30 August 2015}}</ref> who introduced fourteen new constellations.<ref>{{cite web |url= http://www.ianridpath.com/startales/startales1d.html#lacaille |title=Nicolas Louis de Lacaille at the Cape|author=Ian Ridpath |access-date=4 July 2022}}</ref> Lacaille studied the stars of the southern hemisphere from 1751 until 1752 from the [[Cape of Good Hope]], when he was said to have observed more than 10,000 stars using a [[refracting telescope]] with an aperture of {{convert |0.5|in|mm}}.

In 1922, [[Henry Norris Russell]] produced a list of 88 constellations with three-letter abbreviations for them.<ref>{{cite web| url = http://www.ianridpath.com/iaulist1.html| title = The original names and abbreviations for constellations from 1922| access-date = 31 January 2010}}</ref> However, these constellations did not have clear borders between them. In 1928, the IAU formally accepted the 88 modern constellations, with contiguous boundaries<ref>{{cite web| url = http://www.ianridpath.com/boundaries.html| title = Constellation boundaries. | access-date = 24 May 2011}}</ref> along vertical and horizontal lines of [[right ascension]] and [[declination]] developed by [[Eugène Joseph Delporte|Eugene Delporte]] that, together, cover the entire celestial sphere;<ref name="auto"/><ref name="Lachièze-ReyLuminet2001">{{cite book|author1=Marc Lachièze-Rey|author2=Jean-Pierre Luminet|author3=Bibliothèque Nationale de France. Paris|title=Celestial Treasury: From the Music of the Spheres to the Conquest of Space|url=https://books.google.com/books?id=0ZFXiNn62ZEC&pg=PA80|date=2001|publisher=Cambridge University Press|isbn=978-0-521-80040-2|page=80}}</ref> this list was finally published in 1930.<ref name="IAU1928"/> Where possible, these modern constellations usually share the names of their Graeco-Roman predecessors, such as Orion, Leo, or Scorpius. The aim of this system is area-mapping, i.e. the division of the celestial sphere into contiguous fields.<ref name="iau-const" /> Out of the 88 modern constellations, 36 lie predominantly in the northern sky, and the other 52 predominantly in the southern.

{{scalable image|Hipparcos Catalogue equirectangular plot.svg|650px|{{center|Equirectangular plot of declination vs right ascension of stars brighter than apparent magnitude 5 on the [[Hipparcos Catalogue]], coded by spectral type and apparent magnitude, relative to the modern constellations and the ecliptic}}}}

The boundaries developed by Delporte used data that originated back to epoch [[epoch (astronomy)#Besselian years|B1875.0]], which was when [[Benjamin A. Gould]] first made his proposal to designate boundaries for the celestial sphere,<ref>{{cite web|work = Star Tales
|url= http://www.ianridpath.com/startales/gould.html
|title=Benjamin Apthorp Gould and the ''Uranometria Argentina''
|author=Ian Ridpath}}</ref> a suggestion on which Delporte based his work. The consequence of this early date is that because of the [[precession (astronomy)|precession]] of the [[equinox]]es, the borders on a modern star map, such as epoch [[J2000]], are already somewhat skewed and no longer perfectly vertical or horizontal.<ref>A.C. Davenhall & S.K. Leggett, [http://cdsarc.u-strasbg.fr/ftp/cats/VI/49/constell.pdf "A Catalogue of Constellation Boundary Data"], (Centre de Donneés astronomiques de Strasbourg, February 1990).</ref> This effect will increase over the years and centuries to come.