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The
Astrolabe
A Portable Calculator and Measuring Tool
Astrolabes
served as mechanical maps of the Universe. Sophisticated,
hand-held instruments, they were used for centuries to teach
people about the sky. The back side had a moveable sighting
arm and a scale of degrees for measuring altitude. The front
side was engraved with a flattened map of the heavens, which
was used with other moveable parts to solve practical astronomical
problems.
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Islamic
Astrolabe, 1090 A.D.
This astrolabe has several interchangeable plates, each engraved
with the celestial coordinates for a different latitude. The
pointers on the top plate indicate the positions of 22 bright
stars. The top plate can rotate to show where those stars
will appear at different times or dates, much like a modern
paper or plastic star finder. The instrument could also be
used to predict when the Sun or certain bright stars would
rise or set on any date.
Lent by the National Museum of American History
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French
Astrolabe, circa 1600s
When this astrolabe was suspended from the ring at the top,
the sighting arm and scale of degrees on the back could be
used to measure the height of the Sun or a star above the
horizon. Such measurements could be used to determine latitude
or the time of day or night. This astrolabe was made about
six centuries after the one above. Has the basic design changed
much?
Lent by the National Museum of American History
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Islamic
Celestial Globe, 1630 A.D.
This brass globe served both as a map of the heavens,
as viewed from outside the starry sphere, and as a precision
tool for making astronomical calculations. Engraved on its
surface are various coordinate lines, constellation figures,
and Arabic inscriptions. The stars are made of embedded bits
of silver. The globe is hollow and was cast in one seamless
piece. It was originally set in a cradle of rings, which depicted
the horizon and other astronomical circles.
Lent by the National Museum of American History |
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The
Quadrant
A Precision Tool for Mapping the Heavens
Quadrants were used to measure altitudes of celestial objects
and were especially useful for mapping the sky. They consisted
of a sighting device mounted on a quarter circle, or quadrant,
which was engraved with degree markings. Quadrants ranged
in size from small hand-held or table-mounted versions to
large mural quadrants mounted on walls.
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Quadrant
Astrolabe, circa 1325 A.D.
This rare instrument-only seven dating from medieval times
are known to exist-combines the features of a quadrant and
an astrolabe. Essentially, the circular face of an astrolabe
has been "folded over" twice to create a quarter-circle.
This instrument could serve as a measuring tool and perform
many of an astrolabe's calculation functions as well.
Lent by the National Museum of American History
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Other
Featured Artifacts in this section of the exhibit:
Tycho Armillary Sphere
Return
to: Exploring The Universe with the Naked
Eye
Next: Looking Further: Exploring The
Universe with Telescopes
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