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Calculating Coptic Orthdox Easter
This manuscript deals with the calculation of Easter Sunday according to the Coptic calendar. Fixing this date each year governs much of the liturgical and devotional life of the Coptic Orthodox Church. The Coptic calendar begins in 284 AD, which is called Anno Martyrum (AM), or Year of the Martyrs. The first folio contains a table of the four seasons with their corresponding Coptic months and zodiacal signs. The following pages, some of which are torn or badly stained, provide instructions for calculating the movement of the moon and reconciling ...
The Book of Remedies from Deficiencies in Setting Up Marble Sundials
This work is a treatise for timekeepers (singular muwaqqit), and discusses the telling of time from such astronomical observations as the sun’s angle of inclination (mayl), altitude (irtifā‛), as well as the direction (samt) and length of cast shadows (zill). In 14 chapters, the author goes through methods for the computation of these factors, determination of the direction of prayer (qibla), and time of the day. He observes that using instruments (ālāt), such as markings on the ruler (mistara) and the compass (bargār, from the Persian pargār), and geometric ...
Seasonal Almanac Based on the Coptic Calendar
The author of this work, Shaykh al-Islām Ahmad al-Bashtakī, lived in Bashtak near central Cairo. The work goes through the 13 months of the Coptic calendar: Tūt (Thout), Bāba (Paopi), Hātūr (Hathur), Koihak (Koiak), Tūba (Tobi), Imshīr (Meshir), Baremhāt (Paremhat), Barmūda (Paremoude), Bashons (Pashons), Bawna or Būna (Paoni), Ibīb (Epip), Misurī (Mesori), and the Days of Nasī (ayyām al-nasī; also known as the Little Month, Pi Kogi Enavot, or El Nasii). The work gives the corresponding months in the Roman and Persian calendars, notes the astrological significance of days, and ...
Treatise for Observers on Constructing the Circle of Projection
This work is a treatise on the important subject of timekeeping. It is a work of technical astronomy, in 19 folios, that begins by emphasizing the religious significance of knowledge of time. It is divided into an introduction, two chapters, and a conclusion. Comprehensive procedures for the construction of tables and their use are provided. The work was completed in 1473 (878 A.H.).
Compendium on Using the Device Known as the Almucantar Quarter
This work, by a timekeeper at the Al-Azhar Mosque in Cairo, is an important and comprehensive textbook on timekeeping. It introduces the useful device of dividing a quarter of a circle of projection into sections known as almucantars (muqanṭarāt). The work, comprising 100 folio pages, contains 30 chapters and a conclusion. The work was composed in 1440-1 (844 A.H.) and was copied in 1757 (1170 A.H.).
The Travelers Guide on Drawing the Circle of Projection
This is a work on timekeeping and the determination of the direction of prayer (qibla), particularly intended for people who travel. The author, Abu al-‛Abbās Shihāb al-Dīn Ahmad b. Zayn al-Dīn Rajab b. Tubayghā al-Atābakī, known as al-Majdī or Ibn al-Majdī (1366-1447 [767-850 A.H.]), was descended from a powerful family with ties to Mamlūk rulers and was a renowned and prominent mathematician, geometrician, and astronomer. He served as the timekeeper of the Al-Azhar Mosque. This work is an abridgment of his other major book, Irshād al-ḥā’ir ilā ...
Maximum Benefit from the Knowledge of Circles of Projection on the 30 Degree Northern Latitude
This work, a treatise on practical astronomy, deals with such issues as timekeeping and determining the proper direction of prayer. The work begins with a brief introduction, but the bulk of the manuscript contains tables used to determine time. The introductory section contains illustrative examples on how to use the tables.
Deliverance from Error on Knowledge of Times of Day and the Direction of Prayer
This work on elementary knowledge of practical astronomy begins by emphasizing the religious significance of knowing how to keep the time and how to determine the proper direction of prayer (qibla). It describes the conventional correspondence between ordinal numbers and the letters of the Arabic alphabet. It then enumerates, and goes through, the names of the months in the lunar Arabic calendar and in the solar Coptic calendar. It highlights certain important dates, such as the beginning of the New Year, and introduces the 12 zodiacal signs. The front page ...
A Treatise on Zodiacal Signs and Constallations: Unique Jewels on the Benefits of Keeping Time
This work is an introductory, but well-organized, treatise on the elements of time-keeping and reckoning. The treatise is divided into seven sections and a conclusion. It introduces the Arabic, Coptic, and Syriac (or Alexandrian) calendars, and comments on the Persian, Roman, and Hebraic calendars. The work gives the names and lengths of the months in various calendars, explains the different methods for ascertaining the beginnings of years and months, discusses the signs of the zodiac and their relation to the four seasons, and describes the apparent motion of the sun ...
The Book of the Table Regarding the Knowledge of the Time and the Heavens for the Calculation of the Beginning of the Islamic and Christian Months
Because of the religious obligation to perform canonical prayers at set times of the day and the sanctity attributed to particular times of the year, such as the month of Ramaḍān, Muslim scientists have studied questions relating to the calendar and the reckoning of time almost since the beginning of Islam. The present manuscript presents tables for the comparison of the Hijrī and Christian years. Little is known of the author of these tables, al-Ḥusayn ibn Zayd ibn ‘Alī ibn Jaḥḥāf, beyond a marginal note, which states that Ibn Jaḥḥāf ...
The Lights of the Stars
The present manuscript is a commentary entitled Anwār al-nujūm (The lights of the stars) by an author who appears to have stated his name as Jamist al-Rumi (Jamist the Byzantinian). The work is based on Al-zīj al-jadīd (The new astronomical tabulations) by Alī ibn Ibrāhīm Ibn al-Shāṭir (died 1375), the most-distinguished Muslim astronomer of the 14th century. Ibn al-Shāṭir was active as muwaqqit (timekeeper) at the Umayyad mosque in Damascus, where he constructed a magnificent sundial to adorn the central minaret; it had special curves to measure the times ...