Many instruments have been called 'astrolabes' through the centuries. The name comes from the Greek meaning 'star taker'. The instrument that is most commonly referred to by the name astrolabe is more properly called a planispheric astrolabe. It's an instrument that is essentially a computer -- or maybe more accurately a circular slide rule -- that displays the sky.
The astrolabe came in many different forms with the earliest existing examples coming from about the year 1000, though various descriptions exist that suggest they have existed much longer. A typical model would have a series of plates that each represent a single latitude. The plate shows the horizon and has markings to show how high something is above the horizon and it's position east and west (the azimuth). This is overlaid by a 'rete' (Latin for 'net') that has pointers for the positions of stars. By positioning a given star (or sun) at it's observed position. The astrolabe is then set for the condition of the sky at the time of the observation. It doesn't have the ability to show where the planets are, however. The position of the sun can be determined by from a calendar scale found on the back and then set with a rule on the front.
A properly set astrolabe can tell time (day or night), sunrise, sunset, twilight, astrological measurements, star rise & set times, among other readings. It can also be used for some surveying measurements such as measuring the height of a structure. Islamic astrolabes frequently had markings to determine prayer times and the direction to Mecca.
For detailed information on astrolabes, check out Jim Morrison's astrolabe site in the related links.
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Astrolabe
The astrolabe was invented sometime in the first or second century BC.
The astrolabe is a very ancient astronomical computer for solving problems relating to time and the position of the Sun and stars in the sky. Several types of astrolabes have been made. By far the most popular type is the planispheric astrolabe, on which the celestial sphere is projected
An Astrolabe
compass, and the astrolabe
== == the astrolabe is to find the altitude of a stellar object
The word astrolabe is a noun. The plural is astrolabes.
astrolabe=star+mechanical clock
Astrolabe: star + Mechanical Clock
An astrolabe is an old instrument used to calculate the position of celestial bodies. Here are some sentences.I found an antique astrolabe in an old store.An astrolabe was used before the sextant was invented.Polish that astrolabe so it doesn't tarnish.
An astrolabe helped sailors because it could determine any direction based on the position of the stars. This is why the astrolabe helped sailors.
The scientist used an astrolabe to find the altitude of the sun and stars.
what does aastrolabe
The astrolabe must be level in order to read the altitudeproperly.
To read an astrolabe, level the plum bob, the degree scale, the altitude, and the protractor.
Cartography navigational compass astrolabe aircraft