EARLY ASTROLABES

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The theory of the astrolabe was written about by Hipparchus in the 2nd century BC and added to in later centuries.
True astrolabes were built by Greeks by the 7th century. The Greek-invented astrolabe had a plate and a rotating part called a rete. It was used by astrologers to measure the angle to stars, “wandering stars“ and the sun in the sky. It could determine the time in the day or at night, and was used in land navigation to determine directions and latitude.
In the 7th century, when what is now Syria and Iraq were part of the former eastern Roman Empire that had become the Byzantine Empire, the Christian bishop Severus Sebokht (575 – 667), who lived in what is now Iraq, wrote in the Syriac language a treatise on the astrolabe.

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Thipparchos_1

Hipparchus invented the astrolabe in the 2nd century BC.

ANCIENT OBSERVATORIES
Muslims were not the first to establish an astronomical observatory. The ancient Babylonian calculation of the length of the month was off by only nine-tenths of a second per month and was not improved upon until modern times. http://en.wikipedia.org/wiki/Lunar_theory

GREEK ASTROLABES
The theory of the astrolabe was written about by Hipparchus in the 2nd century BC and added to in later centuries.
True astrolabes were built by Greeks by the 7th century. The Greek-invented astrolabe had a plate and a rotating part called a rete. It was used by astrologers to measure the angle to stars, “wandering stars“ and the sun in the sky. It could determine the time in the day or at night, and was used in land navigation to determine directions and latitude.
In the 7th century, when what is now Syria and Iraq were part of the former eastern Roman Empire that had become the Byzantine Empire, the Christian bishop Severus Sebokht (575 – 667), who lived in what is now Iraq, wrote in the Syriac language a treatise on the astrolabe.
Al-Farghani (early 9th century),, al-Saghani (930? – 990), Ibn al‐Samh (979 – 1035),  Shihab Al-din Ahmed ibn Abi Bakr as-Sarraj Al-Hamawi (1270? – 1328) also wrote books about how to construct and use the Greek-invented astrolabe or quadrant.

EQUATORIUM
Al-Zarqālī borrowed 5th century instructions from Proclus on how to build an equatorium https://en.wikipedia.org/wiki/Equatorium for calculating the position of the sun or planets using diagrams of the Ptolemaic model.

CELESTIAL GLOBES
Thales of Miletus built a celestial globe http://www.britannica.com/science/celestial-globe in the 6th century BC. A celestial globe is a sphere on which are marked points representing the apparent location of the stars as they appear in the sky.
This plotting of stars as points onto a celestial globe is called orthographic projection.

DEMONSTRATIONAL ARMILLARY SPHERE
Greeks built a demonstrational armillary sphere which reproduced the daily rotation of the sun, moon and five planets mechanically.

SPHERES AND GLOBES AS PLOTTING DEVICES
Hipparchus in the 2nd century BC plotted stars onto a smooth celestial globe, which is called orthographic projection.
http://en.wikipedia.org/wiki/Orthographic_projection  To measure coordinates on his smooth celestial globe, he built an armillary sphere consisting of a skeleton of 4 circular bands (probably for the equator, the apparent path of the sun, and 2 meridian circles linking the poles). The number of bands on an armillary sphere varies,
Al-Battani (859 – 929) placed a 4 ring skeleton of the armillary sphere of Hipparchus over the celestial globe of Hipparchus, thereby making the plotting of dots (to represent stars) more accurate
[Confusingly, the armillary sphere open framework is sometimes called a spherical astrolabe, but the armillary sphere is a device used in plotting orthographic projection, and is not an astrolabe (which is a device for viewing things in the sky), but can be used to view stars and planets by adding a viewing tube (with no lens).
Greek-speaking Ptolemy in the 3nd century Roman Empire colony of Alexandria Egypt wrote about the armillary sphere.
Al-Nayrizi (865–922) was a Persian astronomer who wrote commentaries on Ptolemy, and wrote about the armillary sphere.

SPHERE OF PTOLEMY
The theory of the astrolabe was written about by Hipparchus in the 2nd century BC and added to in later centuries.
True astrolabes were built by Greeks by the 7th century. The Greek-invented astrolabe had a plate and a rotating part called a rete. It was used by astrologers to measure the angle to stars, “wandering stars“ and the sun in the sky. It could determine the time in the day or at night, and was used in land navigation to determine directions and latitude.

PARALLACTIC RULER (TRIQUETRUM)
In the 2nd century, Ptolemy invented the
triquetrum (parallactic ruler) mechanical device for measuring the altitude of heavenly objects.  
https://en.wikipedia.org/wiki/Triquetrum_(astronomy)

Later, Muslims wrote about it.

Image from de.wikipedia, via Wikimedia Commons.

Image credit https://commons.wikimedia.org/wiki/File:Hipparchos_1.jpeg#mw-jump-to-license


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