Almucantar
circle on the celestial sphere parallel to the horizon
An almucantar (also spelled almucantarat or almacantara) is a circle on the celestial sphere parallel to the horizon. Two stars that lie on the same almucantar have the same altitude.
The term was introduced into European astronomy by monastic astronomer Hermann Contractus of Reichenau, Latinized from the Arabic word al-muqanṭarah ("the almucantar, sundial", plural: al-muqanṭarāt), derived from qanṭarah ("arch, bridge")
Almucantar staff
An almucantar staff is an instrument chiefly used to determine the time of sunrise and sunset, in order to find the amplitude and consequently the variations of the compass. Usually made of pear tree or boxwood, with an arch of 15° to 30°, it is an example of a backstaff.
The sun casts that shadow of a vane (B in the adjacent image) on a horizon vane (A). The horizon vane has a slit or hole to allow the observer to see the horizon in the distance. The observer aligns the horizon and shadow so they show at the same point on the horizon vane and sets the sighting vane (C) to align his line of sight with the horizon. The altitude of the sun is the angle between the shadow vane and the sighting vane (B-A-C).
Solar almucantar
The almucantar plane that contains the Sun is used to characterize multiple scattering of aerosols. Measurements are carried out rapidly at several angles at both sides of the Sun using a spectroradiometer or a photometer.
This brief starts where responsible research should: with the source description of “Almucantar” as circle on the celestial sphere parallel to the horizon. Everything that follows is an evidence route, not borrowed authority.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated May 17, 2026. The linked authority identifier is Q686281. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Almucantar” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.