Editing Angle (section)

==Angles in geography and astronomy==
In [[geography]], the location of any point on the Earth can be identified using a ''[[geographic coordinate system]]''. This system specifies the [[latitude]] and [[longitude]] of any location in terms of angles subtended at the center of the Earth, using the [[equator]] and (usually) the [[Greenwich meridian]] as references.

In [[astronomy]], a given point on the [[celestial sphere]] (that is, the apparent position of an astronomical object) can be identified using any of several ''[[astronomical coordinate systems]]'', where the references vary according to the particular system. Astronomers measure the ''[[angular separation]]'' of two [[star]]s by imagining two lines through the center of the [[Earth]], each intersecting one of the stars. The angle between those lines and the angular separation between the two stars can be measured.

In both geography and astronomy, a sighting direction can be specified in terms of a [[vertical angle]] such as [[altitude angle|altitude]] /[[elevation angle|elevation]] with respect to the [[horizon]] as well as the [[azimuth]] with respect to [[north]].

Astronomers also measure objects' ''apparent size'' as an [[angular diameter]]. For example, the [[full moon]] has an angular diameter of approximately 0.5° when viewed from Earth. One could say, "The Moon's diameter subtends an angle of half a degree." The [[small-angle formula]] can convert such an angular measurement into a distance/size ratio.

Other astronomical approximations include:
* 0.5° is the approximate diameter of the [[Sun]] and of the [[Moon]] as viewed from Earth.
* 1° is the approximate width of the [[little finger]] at arm's length.
* 10° is the approximate width of a closed fist at arm's length.
* 20° is the approximate width of a handspan at arm's length.
These measurements depend on the individual subject, and the above should be treated as rough [[rule of thumb]] approximations only.

In astronomy, [[right ascension]] and [[declination]] are usually measured in angular units, expressed in terms of time, based on a 24-hour day.
{|class="wikitable" 
|-
! Unit !! [[Sexagesimal|Symbol]] !! Degrees !! Radians !! Turns !! Other
|-
! Hour
| h || 15° || {{frac|{{pi}}|12}} rad || {{frac|1|24}} turn ||
|-
! Minute
| m || 0°15′ || {{frac|{{pi}}|720}} rad ||{{frac|1|1,440}} turn || {{frac|1|60}} hour 
|-
! Second
| s || 0°0′15″ || {{frac|{{pi}}|43200}} rad || {{frac|1|86,400}} turn || {{frac|1|60}} minute
|}