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search The celestial sphere with the zenith and almucantar
marked in red, the horizon in green, and the path of a star or
the Sun in blue.  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, from the
Arabic word al-muqantarat, meaning "crooked, bow-like."
Almucantar staff[edit]  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°,[1] it is an example of a backstaff.  This is a
drawing of an almucantar staff. There are three vanes - the
horizon vane (A), the shadow vane (B) and the sighting vane (C).
The sun casts that shadow of a van