Astrolabe in the context of "Star chart"

Hypatia (born c. 350–370 – March 415 AD) was a Neoplatonist philosopher, astronomer, and mathematician who lived in Alexandria, at that time in the province of Egypt and a major city of the Eastern Roman Empire. In Alexandria, Hypatia was a prominent thinker who taught subjects including philosophy and astronomy, and in her lifetime was renowned as a great teacher and a wise counselor. Not the only fourth century Alexandrian female mathematician, Hypatia was preceded by Pandrosion. However, Hypatia is the first female mathematician whose life is reasonably well recorded. She wrote a commentary on Diophantus's thirteen-volume Arithmetica, which may survive in part, having been interpolated into Diophantus's original text, and another commentary on Apollonius of Perga's treatise on conic sections, which has not survived. Many modern scholars also believe that Hypatia may have edited the surviving text of Ptolemy's Almagest, based on the title of her father Theon's commentary on Book III of the Almagest.

Hypatia constructed astrolabes and hydrometers, but did not invent either of these, which were both in use long before she was born. She was tolerant toward Christians and taught many Christian students, including Synesius, the future bishop of Ptolemais. Ancient sources record that Hypatia was widely beloved by pagans and Christians alike and that she established great influence with the political elite in Alexandria. Toward the end of her life, Hypatia advised Orestes, the Roman prefect of Alexandria, who was in the midst of a political feud with Cyril, the bishop of Alexandria. Rumors spread accusing her of preventing Orestes from reconciling with Cyril and, in March 415 AD, she was murdered by a mob of Christians led by a lector named Peter.

Medieval Islamic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age (9th–13th centuries), and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and later in the Far East and India. It closely parallels the genesis of other Islamic sciences in its assimilation of foreign material and the amalgamation of the disparate elements of that material to create a science with Islamic characteristics. These included Greek, Sassanid, and Indian works in particular, which were translated and built upon.

Islamic astronomy played a significant role in the revival of ancient astronomy following the loss of knowledge during the early medieval period, notably with the production of Latin translations of Arabic works during the 12th century.

Ammonius Hermiae (/əˈmoʊniəs/; Ancient Greek: Ἀμμώνιος ὁ Ἑρμείου, romanized: Ammōnios ho Hermeiou, lit. 'Ammonius, son of Hermias'; c. 440 – between 517 and 526) was a Greek philosopher from Alexandria in the eastern Roman empire during Late Antiquity. A Neoplatonist, he was the son of the philosophers Hermias and Aedesia, the brother of Heliodorus of Alexandria and the grandson of Syrianus. Ammonius was a pupil of Proclus in Roman Athens, and taught at Alexandria for most of his life, having obtained a public chair in the 470s.

According to Olympiodorus of Thebes's Commentaries on Plato's Gorgias and Phaedo texts, Ammonius gave lectures on the works of Plato, Aristotle, and Porphyry of Tyre, and wrote commentaries on Aristotelian works and three lost commentaries on Platonic texts. He is also the author of a text on the astrolabe published in the Catalogus Codicum Astrologorum Graecorum, and lectured on astronomy and geometry. Ammonius taught numerous Neoplatonists, including Damascius, Olympiodorus of Thebes, John Philoponus, Simplicius of Cilicia, and Asclepius of Tralles. Also among his pupils were the physician Gessius of Petra and the ecclesiastical historian Zacharias Rhetor, who became the bishop of Mytilene.

A quadrant is an instrument used to measure angles up to 90°. Different versions of this instrument could be used to calculate various readings, such as longitude, latitude, and time of day. It was first proposed by Ptolemy as a better kind of astrolabe. Several different variations of the instrument were later produced by medieval Muslim astronomers. Mural quadrants were important astronomical instruments in 18th-century European observatories, establishing a use for positional astronomy.

The mariner's astrolabe, also called sea astrolabe, was an inclinometer used to determine the latitude of a ship at sea by measuring the sun's noon altitude (declination) or the meridian altitude of a star of known declination. Not an astrolabe proper, the mariner's astrolabe was rather a graduated circle with an alidade used to measure vertical angles. They were designed to allow for their use on boats in rough water and/or in heavy winds, which astrolabes are ill-equipped to handle. It's notable for its role during the Age of Exploration where Portuguese and Spanish navigators used it to great success. In the sixteenth century, the instrument was also called a ring.

Brass is an alloy of copper and zinc, in proportions which can be varied to achieve different colours and mechanical, electrical, acoustic and chemical properties, but copper typically has the larger proportion, generally 2⁄3 copper and 1⁄3 zinc. In use since prehistoric times, it is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure.

Brass is similar to bronze, a copper alloy that contains tin instead of zinc. Both bronze and brass may include small amounts of a range of other elements including arsenic, lead, phosphorus, aluminium, manganese and silicon. Historically, the distinction between the two alloys has been inconsistent, and increasingly museums use the more general term "copper alloy".

A Treatise on the Astrolabe is a mediæval instruction manual on the astrolabe, completed by Geoffrey Chaucer in 1391. Notable as technical prose from a writer better known for poetry, it describes both the form and the proper use of the instrument. It was written in Middle English rather than the more typical Latin.

The treatise is dedicated to Chaucer's son Lowys (Lewis), who was ten during its composition.