Editing Caelum (section)

== Characteristics ==
Caelum is bordered by [[Dorado]] and [[Pictor]] to the south, [[Horologium (constellation)|Horologium]] and [[Eridanus (constellation)|Eridanus]] to the east, [[Lepus (constellation)|Lepus]] to the north, and [[Columba (constellation)|Columba]] to the west. Covering only 125&nbsp;[[square degree]]s, it ranks 81st of the [[88 modern constellations]] in size.

Its main [[asterism (astronomy)|asterism]] consists of four stars, and twenty stars in total are brighter than magnitude&nbsp;6.5<sub>&nbsp;</sub>.<ref name=tirionconst/>

The constellation's boundaries, as set by Belgian astronomer [[Eugène Joseph Delporte|Eugène Delporte]] in 1930, are a 12-sided polygon. In the [[equatorial coordinate system]], the [[right ascension]] coordinates of these borders lie between {{RA|04|19.5}} and {{RA|05|05.1}} and [[declination]]s of {{dec|−27.02}} to {{dec|−48.74}}.<ref name="boundary">{{cite journal | title=Caelum, Constellation Boundary | journal=The Constellations | publisher=International Astronomical Union | url=https://www.iau.org/public/themes/constellations/#cae|access-date=14 January 2014}}</ref> The [[International Astronomical Union]] (IAU) adopted the three-letter abbreviation “Cae” for the constellation in 1922.<ref name="pa30_469">{{cite journal | last=Russell | first=H. N.| title=The New International Symbols for the Constellations | journal=[[Popular Astronomy (US magazine)|Popular Astronomy]] | volume=30 |pages=469–71 |bibcode=1922PA.....30..469R | year=1922}}</ref>

Its main stars are visible in favourable conditions and with a clear southern horizon, for part of the year as far as about the [[41st parallel north]]<ref name=tirionconst>{{cite web| url=http://www.ianridpath.com/constellations1.html | title=Constellations: Andromeda–Indus | work= Star Tales |last=Ridpath |first=Ian |author-link=Ian Ridpath |publisher=self-published | access-date= 1 April 2014}}</ref>{{efn|1=While parts technically reach the horizon to observers between 41°N and [[62nd parallel north|62°N]], stars within a few degrees of the horizon are to all intents and purposes unobservable.<ref name=tirionconst/>}}

These stars avoid being engulfed by daylight for some of every day (when above the horizon) to viewers in mid- and well-inhabited higher latitudes of the Southern Hemisphere. Caelum shares with (to the north) Taurus, Eridanus and Orion midnight culmination in December (high summer), resulting in this fact.  In winter (such as June) the constellation can be observed sufficiently inset from the horizons during its rising before dawn and/or setting after dusk as it culminates then at around mid-day, well above the sun.  In South Africa, Argentina, their sub-tropical neighbouring areas and some of Australia in high June the key stars may be traced before dawn in the east; near the equator the stars lose night potential in May to June; they ill-compete with the Sun in northern tropics and sub-tropics from late February to mid-September with March being unfavorable as to post-sunset due to the light of the [[Milky Way]].