Editing Culmination (section)

{{Short description|The passage of an astronomical body across the meridian}}

In [[observational astronomy]], '''culmination''' is the passage of a [[astronomical object|celestial object]] (such as the [[Sun]], the [[Moon]], a [[planet]], a [[star]], [[constellation]] or a [[deep-sky object]]) across the observer's [[meridian (astronomy)|local meridian]].<ref name="Hoskin1999">{{cite book | author = Michael Hoskin | date = 18 March 1999 | title = The Cambridge Concise History of Astronomy | publisher = Cambridge University Press | pages = | isbn = 978-0-521-57600-0 | url = https://books.google.com/books?id=9gZLXocOnSgC}}</ref>  These events are also known as '''meridian transits''', used in [[timekeeping]] and [[navigation]], and measured precisely using a [[transit telescope]].

During each day, every celestial object [[diurnal motion|appears to move]] along a circular path on the [[celestial sphere]] due to the [[Earth's rotation]] creating two moments when it crosses the meridian.<ref name="cgc">{{cite book |title=The Cambridge Guide to the Constellations |first=Michael E. |last=Bakich |publisher=[[Cambridge University Press]] |year=1995 |page=[https://archive.org/details/cambridgeguideto00baki/page/8 8] |isbn=0521449219 |url-access=registration |url=https://archive.org/details/cambridgeguideto00baki/page/8 }}</ref><ref name="fof">{{cite book |entry=Culmination |page=110 |title=The Facts on File Dictionary of Astronomy |first1=John |last1=Daintith |first2=William |last2=Gould |publisher=Infobase Publishing |year=2009 |isbn=978-1438109329}}</ref>  Except at the [[geographic pole]]s, any celestial object passing through the meridian has an '''upper culmination''', when it reaches its highest point (the moment when it is nearest to the [[zenith]]), and nearly twelve hours later, is followed by a '''lower culmination''', when it reaches its lowest point (nearest to the [[nadir]]). The time of ''culmination'' (when the object culminates) is often used to mean upper culmination.<ref name="cgc" /><ref name="fof" /><ref>{{cite book |entry=Meridian |page=993 |title=The National Encyclopaedia |edition=library |volume=8 |location=London, Edinburgh, and Glasgow |first=William |last=Mackenzie |issue=69 |publisher=Ludgate Hill, E.C. |year=1879–81}}</ref>

An object's [[altitude (astronomy)|altitude]] (''A'') in degrees at its upper culmination is equal to 90 minus the observer's [[latitude]] (''L'') plus the object's [[declination]] (''δ''): 
:{{math|''A'' {{=}} 90° − ''L'' + ''δ''}}.
This equation is the basis for the [[meridian altitude]] method for [[latitude determination]].