almucantar

(ˌælməˈkæntə) or

almacantar

1. (Astronomy) a circle on the celestial sphere parallel to the horizontal plane

2. an instrument for measuring altitudes

[C14: from French, from Arabic almukantarāt sundial]

Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

almucantar

A circle on the celestial sphere that is parallel to the horizontal plane.

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References in periodicals archive ?

In sky-scanning mode, 4STAR measures the diffuse sky radiance at prescribed scattering angles from the sun in the almucantar or principal plane to retrieve aerosol properties (single-scattering albedo, size distribution, and refractive index; see Kassianov et al.

Arctic radiation-icebridge sea and ice experiment: the arctic radiant energy system during the critical seasonal ice transition

I turned over my astrolabe, found Aldebaran on the clear plastic rete, and positioned the star at 41[degrees] in the east on the grid of almucantar circles.

The Astrolabe: astronomy's first hot app: loaded with features, an ancient analog computer replicates the sky's workings

When automatic mode performs, the collimator of sunphotometer tracks the sun each 15 minutes and scans following almucantar (ALM) and solar principle plane (SPP) geometry procedures approximately each hour.

Ground-based polarimetric remote sensing of dust aerosol properties in Chinese deserts near Hexi corridor

Alignment is typically achieved by measuring the altitude of a reference object --either the Sun or a star--using the alidade and then rotating the rete until its projection lies on the appropriate almucantar; it is also necessary to have some sense of east and west in order to know whether to align the object so that it is rising or setting.

Building a model astrolabe

* deformation of local almucantar for astrolabes and similar instruments (Pesek, 1995);