Universal Lamina

The astrolabe (from the Greek astron and labê, meaning “which takes the stars”), an instrument of Greek origin, was adopted as early as the eighth century by the Arabs, who carried out extensive research in the field of astronomy, notably via the translation of Indian, Persian and Greek scientific works, such as Ptolemy’s Almagest. The instrument was much improved between the years 800 and 1100, during which many treatises were written, particularly in the Muslim West. The concept of the “Universal Lamina” appeared in the eleventh century. The device was invented to overcome one of the difficulties of using the planispheric astrolabe, which required a specific tympanum for each latitude in which the instrument was used, increasing the weight, size and cost of it. Al-Bîrûnî was the first to solve this problem, with a projection of the celestial sphere onto the solstitial colure; but it was in Muslim Spain that the instrument was made, very probably by the astronomer Abû al-Hasan ‘Alî ibn Khalaf. It was then improved by Ibrâhîm ibn Yahia al-Naqqâsh al-Tulayteli (from Toledo) known as ibn Zarqâli, who, among other modifications, got rid of the rete.

Like other instruments of its kind, this universal lamina is equipped with a rete, which is divided into two halves, one representing a map of the stars, in which the outer circle represents the equator; the other bearing the usual stereographic projections. On the back, signed by the maker, engravings show the graduations of a concentric zodiacal calendar, a diagram of the unequal hours, a diagram of the sinus and cosinus, a shadow square, and the usual degree markings. The shape of the throne resembles those of the first Muslim astrolabes that originated in Egypt and Syria, while the alidade is like those found on the different types of Moroccan astrolabes. Contrary to the representations of the tropic of Capricorn on conventional retes, the rete of this lamina shows the equator.

Another example of a universal astrolabe signed by Ahmad ibn Sarrâj, made in 1329 and which comes from Aleppo, is kept in the Benaki Museum of Athens. The contemporaneousness of these astronomers and their works illustrates the scientific and cultural coming together between the West and the Muslim West. The universal lamina also reflects an aspect of mutual influence between Muslim and European astronomy. The tradition of universal astrolabes continued into the Middle Ages in the Muslim and Christian West. Alphonso X of Castile’s Libros del saber, written in Castilian around 1276, sets out a detailed explanation of the making of the instrument and its use. This type of instrument was made in 1274 by the Granada astronomer Ibn Basô, who blended the Toledo school with the Syrian traditional school of Damascus, founded by astronomer Habash al-Hasib (ninth century)[1]. On an astrolabe from the Ottoman era, from 1686, the Syrian oriental lamina adopts the western lamina of al-Andalus.