LATE ASTROLABES

astrolab

To see my menu of all Muslim science posts, click https://muslimscience.blog/2016/08/10/mymenu/

A latter 16th-century astrolabe with the typical ‘tulip’ rete associated with the Arsenius workshop.
Image by en.wikipedia User:Isis, via Wikimedia Commons.
image credit https://commons.wikimedia.org/wiki/File:Astrolab.JPG#mw-jump-to-license

 front_of_quadrant-1-1276x957

modern reconstruction of a sine quadrant

Image by Triezel327 at English Wikipedia, via Wikimedia Commons.
image credit https://en.wikipedia.org/wiki/File:Front_of_Quadrant.JPG


SIGHTING TUBE
Astronomers in 10th century Muslim Spain attached sighting tubes (with no lenses) to large armillary spheres.

HINDU ASTROLABES
Ibrahim al-Fazari (717? – 777) and his son Muhammad al-Fazari (740? – 801) helped translated Hindu books about the astrolabe into Arabic and Persian.

JEWISH ASTROLABE
Masha’allah ibn Atharī (740 – 815) was a late 8th century Jewish astrologer and astronomer who converted to Islam. He wrote a treatise on the astrolabe.

SHADOW SQUARE
Al-Khwarizmi added to the Greek-invented astrolabe the Greek-invented shadow square (which used the angle and the distance to calculate the height of a hill), star charts to assist in locating a particular star, and markings to show the times of the day to pray, and the direction to pray.
[The “shadow” was a trigonometric function similar to the modern tangent.]

SINE QUADRANT (SINICAL QUADRANT)
Early 9th century Muslim Persian Al-Khwarizmi’s sine quadrant could determine the apparent positions of any celestial object for any time. It consisted of a quarter of a circle divided by marks numbered both 0 to 90 and 90 to 0. It had a plumb line and a grid that looked like graph paper. He added to the Greek-invented astrolabe markings to show the times of the day to pray, and the direction to pray. He also added star charts.  
https://en.wikipedia.org/wiki/Sine_quadrant

MEASURING EARTH’S TILT
To directly measure the obliquity of the ecliptic (tilt of the Earth’s axis, but he did not know that), the late 10th century astronomer Abu-Mahmud Khojandi invented a device that he called the al-Fakhri sextant.

SEXTANTS AND QUADRANTS
If the instrument covered only 60 degrees it was called a sextant. If it covered only 90 degrees, it was called a quadrant. If it was only used to tell time, it was called a horary quadrant. Muslims did not invent sextants, quadrants or horary quadrants.

HORARY (TIME) QUADRANT
The horary quadrant was invented in northern India or Nepal. It was used to determine the time of day from the angle to the sun. It sometimes had 2 sets of markings, so time in either type of hour ( 1/24 of 24 hours, or 1/12 of the time from sunrise to sunset) could be calculated. It was later used also by Muslims.

14 METER LONG ASTROLABE
Ibn Yunus (950-1009) used a 14-meter long astrolabe to obtain very accurate measurements of star positions, planetary conjunctions and lunar eclipses.

WOMAN WHO MADE ASTROLABES
Al-Majriti (? – 1008) may have taught his daughter Fatima how to make astrolabes. He also adjusted astronomy tables for the latitude of Spain.

TORQUETUM
Although some Muslim astrolabe designs had a rete that was a frame rather than a disc,
The 12th century (1100 – 1150) astronomer Jabir ibn Aflah Jabir ibn Aflah (a different Geber than the alchemist Geber) invented a mechanical device called a torquetum to transform measurements relative to the horizon into measurements relative to the plane of the solar system or relative to the plane of the earth’s equator.

THE OTHER AL-TUSI AND THE ROD
Sharaf al-Dīn al-Tūsī (1130? – 1213) was a teacher of astronomy in Damascus, Aleppo and Mosul.
His staff was a rod with markings like those of an astrolabe and a plumb line. It was less accurate but easier to use than an astrolabe.
One of his students was a Jew.
One of his students taught someone who later taught the 13th century astronomer Nasir al-Din al-Tusi.

AL-TUSI
The Persian scholar Nasir al-Din al-Tusi (1201 – 1274), born a Shia Twelver, was captured by a Mongol army. Al-Tusi made his most important contributions after Hulagu Khan built him in 1259 the Rasad Khaneh observatory in what is now Azerbaijan , so al-Tusi could make accurate astrology predictions. (Hulagu Khan was probably a Nizari Shia Sevener, the same sect as Aga Khan is head of today.)
Al-Tusi wrote Shia Sevener religious writings, but Shia Twelvers claim al-Tusi remained a Twelver and was only pretending to be a Sevener.

LATITUDE SEASONAL ADJUSTMENT
Some designs had engraved curved lines to assist in calculating the latitude for different times of the year.

ANY LATITUDE (UNIVERSAL) ASTROLABE
In the 11th century, astronomers in Muslim Spain invented an astrolabe that could be used at any latitude without switching plates. Most astronomers disliked the universal astrolabe, and continued to use an ordinary astrolabe, switching plates at different latitudes.

LINEAR INTERPOLATION
Jamshīd al-Kāshī’s (1380 – 1429)
mechanical device for linear interpolation of the movement of heavenly bodies was not an “analog computer” as falsely claimed in 2 books written by technology historian Donald Hill but financed by a Pakistani organization.

MARAGHEH OBSERVATORY (UZBEKISTAN)
Shortly after 1424, Ulugh Beg (1394 – 1449) at Maragheh Observatory in what is today Uzbekistan built an eleven meter long sextant (similar to an astrolabe but covering only 60 degrees).
Since his father and grandfather led conquering Mongol armies, he likely was a Shia Sevener.
http://en.wikipedia.org/wiki/Maragheh_observatory
Very large instruments had markings not only for degrees and minutes but also for seconds of arc.
The observatory was destroyed by a group of Muslims 25 years later in 1449.

MURAL QUADRANT
Ptolemy’s used a mural quadrant at Alexandria Egypt. This instrument is also called a plinth.
Taqi al-Din built a 90 degree quadrant into a wall of a building, which is called a mural quadrant.

ISTANBUL OBSERVATORY
Taqi al-Din completed in 1577 an observatory near Istanbul.
In 1580 the chief Hanafi Sunni sharia law advisor to the Sultan ordered that the observatory near Istanbul must be destroyed, perhaps because it was being used for astrology.

OTHER TYPES OF ASTROLABES
See the navigation and surveying page for astrolabes used in navigation.
An excellent explanation of various types of astrolabes is at http://catalogue.museogalileo.it/indepth/Astrolabe.html

 

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