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Webster 1913 Edition
Astrolabe
As′tro-labe
(ăs′trō̍-lāb)
, Noun.
[OE.
astrolabie
, astrilabe
, OF. astrelabe
, F. astrolabe
, LL. astrolabium
, fr. Gr. ἀστρολάβον
; ἄστρον
star + [GREEK], [GREEK], to take.] 1.
(Astron.)
An instrument for observing or showing the positions of the stars. It is now disused.
☞ Among the ancients, it was essentially the armillary sphere. A graduated circle with sights, for taking altitudes at sea, was called an astrolabe in the 18th century. It is now superseded by the quadrant and sextant.
2.
A stereographic projection of the sphere on the plane of a great circle, as the equator, or a meridian; a planisphere.
Whewell.
Webster 1828 Edition
Astrolabe
AS'TROLABE
,Noun.
1.
An instrument formerly used for taking the altitude of the sun or stars at sea.2.
A stereographic projection of the sphere, either upon the plane of the equator, the eye being supposed to be in the pole of the world; or upon the plane of the meridian, the eye being in the point of intersection of the equinoctial and the horizon.3.
Among the ancients, the same as the modern armillary sphere.