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Abū Isḥāq Ibrāhīm ibn Yaḥyā al-Naqqāsh al-Zarqālī al-Tujibi[2] (Arabic: إبراهيم بن يحيى الزرقالي); also known as Al-Zarkali or Ibn Zarqala (1029–1100), was an Arab maker of astronomical instruments and an astrologer from the western part of the Islamic world.[2]

Key Information

Although his name is conventionally given as al-Zarqālī, it is probable that the correct form was al-Zarqālluh.[3] In Latin he was referred to as Arzachel or Arsechieles, a modified form of Arzachel, meaning 'the engraver'.[4] He lived in Toledo, Al-Andalus before moving to Córdoba later in his life. His works inspired a generation of Islamic astronomers in Al-Andalus, and later, after being translated, were very influential in Europe. His invention of the Saphaea (a perfected astrolabe) proved very popular and was widely used by navigators until the 16th century.[5]

The crater Arzachel on the Moon is named after him.[4]

Life

[edit]

Al-Zarqālī, of Arab origin,[6][7][8] was born in a village near the outskirts of Toledo, the then capital of the newly established Taifa of Toledo. He started work after 1048 under Said al-Andalusi for the Emir Al-Mamun of Toledo and also under Al-Mu'tamid of the Taifa of Seville. Assuming a leading position under Said, Al-Zarqālī conducted solar observations for 25 years from 1050.[9]

Art from Toledo in Al-Andalus depicting the Alcázar in the year 976.AD

He was trained as a metalsmith and due to his skills he was nicknamed Al-Nekkach "the engraver of metals". His Latinized name, 'Arzachel' is formed from the Arabic al-Zarqali al-Naqqash, meaning 'the engraver'.[4]

He was particularly talented in geometry and astronomy. He is known to have taught and visited Córdoba on various occasions, and his extensive experience and knowledge eventually made him the foremost astronomer of his time. Al-Zarqālī was also an inventor, and his works helped to put Toledo on the intellectual center of Al-Andalus. He is also referred to in the works of Chaucer, as 'Arsechieles'.[4]

In the year 1085, Toledo was taken by the Christian king of Castile Alfonso VI. Al-Zarqālī and his colleagues, such as Al-Waqqashi (1017–1095) had to flee. It is unknown whether the aged Al-Zarqālī fled to Cordoba or died in a Moorish refugee camp.

His works influenced Ibn Bajjah (Avempace), Ibn Tufail (Abubacer), Ibn Rushd (Averroës), Ibn al-Kammad, Ibn al-Haim al-Ishbili and Nur ad-Din al-Betrugi (Alpetragius).

In the 12th century, Gerard of Cremona translated al-Zarqali's works into Latin. He referred to Al-Zarqali as an astronomer and magician.[4] Ragio Montanous[citation needed] wrote a book in the 15th century on the advantages of the Sahifah al-Zarqalia. In 1530, the German scholar Jacob Ziegler wrote a commentary on one of al-Zarqali's works. In his "De Revolutionibus Orbium Coelestium", in the year 1530, Nicolaus Copernicus quotes the works of al-Zarqali and Al-Battani.[10]

Science

[edit]
A copy of al-Zarqālī's astrolabe as featured in the Calahorra Tower.

Instruments

[edit]

Al-Zarqālī wrote two works on the construction of an instrument (an equatorium) for computing the position of the planets using diagrams of the Ptolemaic model. These works were translated into Spanish in the 13th century by order of King Alfonso X in a section of the Libros del Saber de Astronomia entitled the "Libros de las laminas de los vii planetas".

He also invented a perfected kind of astrolabe known as "the tablet of al-Zarqālī" (al-ṣafīḥā al-zarqāliyya), which was famous in Europe under the name Saphaea.[11][12]

There is a record of an al-Zarqālī who built a water clock, capable of determining the hours of the day and night and indicating the days of the lunar months.[13] According to a report found in al-Zuhrī's Kitāb al-Juʿrāfīyya, his name is given as Abū al-Qāsim bin ʿAbd al-Raḥmān, also known as al-Zarqālī, which has made some historians think that this is a different person.[3]

Theory

[edit]

Al-Zarqali corrected geographical data from Ptolemy and Al-Khwarizmi. Specifically, he corrected Ptolemy's estimate of the width of the Mediterranean Sea from 62 degrees to the correct value of 42 degrees.[10] In his treatise on the solar year, which survives only in a Hebrew translation, he was the first to demonstrate the motion of the solar apogee relative to the fixed background of the stars. He measured its rate of motion as 12.04 arcseconds per year, which is remarkably close to the modern calculation of 11.77 arcseconds.[14] Al-Zarqālī's model for the motion of the Sun, in which the center of the Sun's deferent moved on a small, slowly rotating circle to reproduce the observed motion of the solar apogee, was discussed in the thirteenth century by Bernard of Verdun[15] and in the fifteenth century by Regiomontanus and Peurbach. In the sixteenth century Copernicus employed this model, modified to heliocentric form, in his De Revolutionibus Orbium Coelestium.[16]

Tables of Toledo

[edit]

Al-Zarqālī also contributed to the famous Tables of Toledo, an adaptation of earlier astronomical data by Al-Khwarizmi and Al-Battani, to locate the coordinates of Toledo.[9] His zij and almanac were translated into Latin by Gerard of Cremona in the 12th century, and contributed to the rebirth of a mathematically based astronomy in Christian Europe and were later incorporated into the Tables of Toledo in the 12th century and the Alfonsine tables in the 13th century.[17]

Famous as well for his own Book of Tables, of which many had been compiled. Al-Zarqālī's almanac contained tables which allowed one to find the days on which the Coptic, Roman, lunar, and Persian months begin, other tables which give the position of planets at any given time, and still others facilitating the prediction of solar and lunar eclipses.[18] This almanac that he compiled directly provided "the positions of the celestial bodies and need no further computation", it further simplifies longitudes using planetary cycles of each planet.[9] The work provided the true daily positions of the sun for four Julian years from 1088 to 1092, the true positions of the five planets every 5 or 10 days over a period of 8 years for Venus, 79 years for Mars, and so forth, as well as other related tables.[17][19]

In designing an instrument to deal with Ptolemy's complex model for the planet Mercury, in which the center of the deferent moves on a secondary epicycle, al-Zarqālī noted that the path of the center of the primary epicycle is not a circle, as it is for the other planets. Instead it is approximately oval and similar to the shape of a pignon (or pine nut).[20] Some writers have misinterpreted al-Zarqālī's description of an earth-centered oval path for the center of the planet's epicycle as an anticipation of Johannes Kepler's sun-centered elliptical paths for the planets.[21] Although this may be the first suggestion that a conic section could play a role in astronomy, al-Zarqālī did not apply the ellipse to astronomical theory and neither he nor his Iberian or Maghrebi contemporaries used an elliptical deferent in their astronomical calculations.[22]

Works

[edit]

Major works and publications:

  • Al Amal bi Assahifa Az-Zijia
  • Attadbir
  • Al Madkhal fi Ilm Annoujoum
  • Rissalat fi Tarikat Istikhdam as-Safiha al-Moushtarakah li Jamiâ al-ouroud
  • Almanac Arzarchel

See also

[edit]

Notes

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Further reading

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Al-Zarqali

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Abū Isḥāq Ibrāhīm ibn Yaḥyā al-Naqqāsh al-Tujībī al-Zarqālī (Latin: Arzachel or Azarquiel; c. 1029–1100) was a renowned Andalusian Muslim , , and instrument maker from , celebrated for his advancements in and the design of precise astronomical tools. Born around 1029 in Toledo (or possibly ), al-Zarqālī hailed from a family of craftsmen and was largely self-taught in astronomy, excelling as a skilled in constructing intricate devices. He worked primarily in Toledo under the of Ṣāʿid al-Andalusī, leading a collaborative school of astronomers. Over decades, he conducted meticulous observations, including 25 years of solar data and 37 years of lunar measurements starting in 1061, which formed the basis for correcting Ptolemaic models. His work emphasized empirical precision, such as determining the length of the as approximately 42 degrees and establishing the annual motion of the solar apogee at about 12 arcminutes. Al-Zarqālī's most notable inventions include the ṣafīḥa (universal astrolabe or safiha zarqāliyya), a flat, versatile instrument that could represent the for any latitude, detailed in treatises spanning 100 chapters; an equatorium for planetary calculations around 1080; and a sine quadrant with a movable cursor. He also engineered sophisticated water clocks in Toledo, one of which featured a mechanism accurate enough to remain in use until 1135, and another (al-zarqāla) built in 1048–1049 that integrated planetary indicators. His theoretical contributions advanced planetary models, proposing that the eccentricity of orbits varied over time and suggesting shapes for some epicycles, ideas that prefigured later developments in astronomy. Key publications encompass the Toledan Tables (compiled before 1088 with collaborators, providing solar, lunar, and planetary positions), a on the solar year (Al-Risāla al-Jāmiʿa fī al-Shams, c. 1075–1080), an corrected to 1089, and works on stellar motion and . Al-Zarqālī's legacy extended across Islamic and European scholarly traditions; his tables were translated into Latin by Gerard of Cremona in the , influencing medieval astronomers like and remaining in use for over two centuries until superseded by Copernican models. His innovations in instruments and observations bridged Hellenistic astronomy with later advancements, earning him recognition as one of the foremost scientists of medieval Islamic , with a lunar crater named Arzachel in his honor. He died in on 15 October 1100, reportedly after fleeing Toledo amid Christian reconquest pressures.

Biography

Early Life and Education

Al-Zarqali, also known as Abū Isḥāq Ibrāhīm ibn Yaḥyā al-Naqqāsh, was born around 1029, possibly in or near Toledo or in Córdoba in , to a family of skilled artisans specializing in and instrument crafting, from which he derived his al-Naqqāsh, meaning "the engraver." His family background immersed him in the practical arts of mechanical construction from a young age, fostering an initial aptitude for that would later inform his astronomical innovations. Growing up in 11th-century during the period, Al-Zarqali experienced the socio-political fragmentation following the collapse of the of in 1031, with Toledo emerging as an independent Muslim emirate under the Banu Dhul-Nun dynasty until its conquest by Christian forces in 1085. This era of relative autonomy in the provided a vibrant intellectual environment, marked by patronage of scholars and access to a multicultural hub where , Hebrew, and intersected, facilitating the exchange of knowledge. His early education was largely self-directed and informal, rooted in the artisanal traditions of his family rather than formal scholarly institutions, though he likely drew initial influences from the local Toledan community of astronomers and translators who preserved and adapted Greek and Ptolemaic texts into . By his early twenties, Al-Zarqali had established a reputation as a proficient maker of astronomical instruments, honing his skills through practical before delving deeper into around age 30. This foundational training in crafting distinguished him among contemporaries and set the stage for his later collaborations in Toledo's scientific circles.

Career and Observations

Al-Zarqali began his professional career in Toledo around 1048, serving under the patronage of Emir Al-Mamun ibn Dhunnun of the during the 1060s, where he was tasked with crafting astronomical instruments for a major research initiative led by court astronomers. He later entered the service of , ruler of the , performing duties as a court astrologer that involved predicting celestial events to advise on political and agricultural matters. In Toledo, Al-Zarqali assumed a leadership role within the Toledo School of Astronomers, a collaborative group fostered under Al-Mamun's court that built on earlier traditions established by figures like . He worked closely with contemporaries such as Ibn al-Samḥ, al-Kirjānī, and Saʿīd al-Andalusī, contributing to joint efforts in refining and instrument design to advance astronomical precision in . From 1050 to 1075, Al-Zarqali conducted extensive solar observations in Toledo, spanning 25 years of meticulous on the sun's apparent , inclination of the , and rates, utilizing custom-built instruments to achieve measurements accurate to within arcminutes. He also conducted 37 years of lunar observations starting in 1061. These efforts culminated in key findings around 1075, including refined solar parameters that corrected earlier Ptolemaic models and informed subsequent planetary theories. The Christian conquest of Toledo by Alfonso VI in 1085 disrupted Al-Zarqali's work, prompting his departure from the city sometime between 1081 and 1085 amid the advancing ; he likely relocated to southern , possibly or . He died on 15 October 1100 in . During his lifetime, Al-Zarqali's innovations in observation and instrumentation directly influenced contemporaries like Ibn Bajjah (), who engaged with and critiqued his solar and planetary models in developing his own astronomical and philosophical frameworks in .

Astronomical Instruments

Astrolabes and Plates

Al-Zarqali, an 11th-century Andalusian astronomer and instrument maker, introduced significant innovations to the , culminating in the invention of the safiha (also known as the safiha zarqaliya or universal astrolabe plate), a flat and portable device designed for use at any latitude without the need for adjusting or replacing the traditional rete (the rotating star map component). This universal plate represented a departure from earlier , which relied on multiple latitude-specific discs, by employing a of the from an equinoctial point rather than the , allowing for broader applicability across diverse geographical locations. His improvements enhanced the instrument's precision and versatility, making it a key tool for solving complex problems in , such as determining altitudes and azimuths of celestial bodies. The safiha zarqaliya consisted of several essential components that facilitated its multifunctional design. At its core was a graduated plate featuring a of the equator, tropics, and horizon circles, inscribed with precise scales for angular measurements and celestial coordinates. Accompanying this were sighting vanes, typically in the form of an (a rotating rule with adjustable sights), which allowed users to align the instrument with stars or the sun for accurate observations. Additional elements included a zodiacal circle for positioning and engraved scales for timekeeping, along with a reference table listing coordinates for 29 principal stars to aid in star positioning and identification. Functionally, the safiha enabled the mechanical resolution of challenges by superimposing the projected celestial features and rotating components to compute positions relative to the observer's horizon. This design permitted calculations of celestial altitudes (vertical angles above the horizon) and azimuths (horizontal angles from north), essential for mapping stellar paths without cumbersome trigonometric computations. Unlike the rete-dependent traditional , the safiha's fixed projection simplified operations for non-specialists while maintaining high accuracy for solar and stellar movements. In practice, Al-Zarqali's safiha found widespread application in for navigation, where it assisted travelers and sailors in determining directions using star altitudes and azimuths during overland and maritime journeys. It also served for time-finding, allowing precise determination of local and prayer timings through horizon alignments and scale readings. Additionally, the instrument supported survey work, enabling surveyors to measure angular distances for land mapping and architectural alignments in regions like Toledo.

Clocks and Sundials

Al-Zarqali constructed an advanced , or clepsydra, in Toledo in the mid-11th century during the reign of the ruler al-Ma'mūn ibn Dhī al-Nūn, likely for use in the palace gardens and public timekeeping. The device consisted of two large basins connected to subterranean pipes that regulated water flow to simulate lunar phases, serving as a precise for astronomical observations and daily timing. As the new moon appeared, water began flowing into the basins at a controlled rate; by the on the fifteenth night, the basins were completely full, after which water drained out proportionally as the moon waned, emptying by the twenty-ninth night. A key innovation in the clock's design was its self-regulating mechanism, which prevented inaccuracies from variable water flow. The basins were made of porous earthenware and placed in larger copper basins. As water seeped through the sides of the earthenware basins, the water level in the copper basins rose and fell in synchronization with the lunar cycle. The inflow was adjusted—if the water drained too rapidly, the supply was increased; if too slowly, it was reduced—to maintain precision. This hydraulic system marked hours and intervals through the rising and falling water levels, providing reliable timekeeping independent of weather conditions, and it remained in operation after the Christian conquest of Toledo in 1085 until at least 1135. The clock's sophistication influenced later European water clocks and demonstrated Al-Zarqali's expertise in integrating hydraulic engineering with astronomy for practical applications. The clock and astrolabes were integrated to facilitate synchronized astronomical observations, allowing Al-Zarqali to correlate solar and lunar time with planetary positions for his extensive solar and lunar recordings.

Equatoria and Quadrants

Al-Zarqali also invented an equatorium around 1080, a mechanical device for computing the positions of based on Ptolemaic models without arithmetic operations. His design incorporated diagrams of eccentric and epicyclic motions and suggested non-circular elements, such as shapes for certain epicycles (e.g., Mercury's described as "like a "), prefiguring later astronomical theories. Additionally, he developed a sine quadrant equipped with a movable cursor (majarra), functioning as a graphical tool for trigonometric calculations, including scales for sines, cosines, and solar declinations. This instrument aided in determining celestial angles, time, directions, and survey measurements, enhancing precision in observational astronomy.

Theoretical Contributions

Planetary Motion and Apogee

Al-Zarqali's groundbreaking analysis of planetary dynamics centered on the solar system, where he provided the first empirical demonstration that the solar apogee moves relative to the fixed stars, challenging the static assumptions in Ptolemy's . Through systematic solar observations conducted over 25 years in Toledo during the mid-11th century, he identified systematic discrepancies in the positions of the Sun's apogee when compared against stellar backgrounds, establishing this motion as distinct from the precession of the equinoxes. This proof relied on precise measurements of solar longitudes at equinoxes and solstices, cross-referenced with earlier data from astronomers like , revealing a gradual shift that could not be explained by observational error alone. Quantifying this phenomenon, Al-Zarqali calculated the apogee's rate as 1° every 279 years, corresponding to approximately 12.9 arcseconds per year—a value close to the modern determination of approximately 11.6 arcseconds per year. This measurement emerged from his integration of Toledo's observational records with theoretical adjustments, highlighting the apogee's westward drift independent of equinoctial . His approach marked a shift toward observation-driven astronomy, as he emphasized the need for long-term data to detect such subtle annual changes. In refining Ptolemaic models, Al-Zarqali incorporated empirical corrections for solar eccentricity and the equation of time, addressing inaccuracies in predicting solar positions that arose from assuming constant parameters. He adjusted the eccentricity to better fit observed solar anomalies, such as variations in the length of daylight, and accounted for the equation of time by linking it to the evolving apogee position, thereby improving the accuracy of solar calendars and predictions. These refinements extended to broader planetary , enabling more reliable forecasts of positions by introducing dynamic elements into geocentric frameworks. The resulting methodology influenced the Toledan Tables, where apogee motion parameters were tabulated for practical use. The implications of Al-Zarqali's work transcended the Sun, as later Islamic astronomers generalized the apogee motion to other , fostering a conceptual evolution toward recognizing variable in the solar system. This laid foundational insights for long-term ephemerides, emphasizing that static models insufficiently captured celestial dynamics over centuries.

Geographical and Trigonometric Advances

Al-Zarqali made significant corrections to ancient geographical measurements, particularly addressing inaccuracies in the works of and . He revised the estimated width of the from Ptolemy's overstated 62° of longitude to a more accurate 42°, based on direct observations using astrolabes in . This adjustment, which built upon Al-Khwarizmi's earlier reduction to 52°, enhanced the precision of regional mapping and navigational calculations. In , Al-Zarqali advanced the computational tools essential for astronomical work by refining sine tables and chord functions, which facilitated the solution of spherical triangles. These improvements allowed for more accurate determinations of celestial positions and angular relationships on the , surpassing the granularity of prior tables compiled by figures like . His tables included values for , cosines, versed sines, secants, and tangents, computed to higher precision for practical use in . Al-Zarqali applied these trigonometric methods to establish latitudes and across , leveraging measurements of stellar altitudes, such as the longitude of . For instance, his observations in Toledo and provided corrected coordinates that aligned local geography with celestial references, aiding in the calibration of instruments independent of specific latitudes. This work supported broader efforts in regional surveying and timekeeping. These geographical and trigonometric innovations were integrated into Al-Zarqali's overarching astronomical framework, influencing the development of universal instruments like the safiha and enhancing the accuracy of predictive models. By embedding refined chord and sine computations into stereographic projections, he enabled versatile applications in both static positional astronomy and dynamic observations, such as those related to apogees.

Astronomical Tables

Development of the Toledan Tables

The development of the Toledan Tables began with observations in the early 1050s and 1070s within the Toledo School of astronomers, a collaborative effort involving approximately 12 scholars, primarily with some , under the patronage of rulers in . This project marked a pinnacle of Andalusian astronomical activity during the fragmented political landscape of the period, where scientific endeavors bolstered cultural and intellectual prestige amid rivalries among petty kingdoms. The initiative built upon earlier Eastern traditions but emphasized empirical refinement tailored to the Iberian context. Central to the tables' creation was the integration of local observations conducted along the meridian of Toledo, which allowed for precise adjustments to inherited data from sources like al-Khwarizmi's Zij al-Sindhind and Ptolemaic models. These observations, spanning decades, addressed discrepancies in planetary positions and timings by incorporating site-specific parameters, such as latitude and longitude, to enhance predictive accuracy for Western longitudes. Al-Zarqali was a key contributor and leader in the effort under Sa'id al-Andalusi until his death in 1070, after which Al-Zarqali continued directing the compilation by overseeing systematic data collection and verification. Al-Zarqali's particular contributions focused on refining solar and lunar eclipse predictions, leveraging his long-term observational records—over 25 years for solar phenomena and 30 years for lunar ones—to calibrate models against actual events. This work ensured the tables' utility for timekeeping and calendrical purposes. Politically, the tables served as tools for astrological advising to Taifa rulers, such as Yahya al-Ma'mun of Toledo (r. 1044–1075), enabling prognostications on governance, warfare, and agriculture to legitimize authority and navigate alliances. In one instance, theoretical inputs like the motion of planetary apogees, derived from Al-Zarqali's studies, informed the underlying parameters without altering the core observational framework.

Content and Methodology

The Toledan Tables, compiled under the direction of Al-Zarqali in 11th-century Toledo, encompass a comprehensive set of astronomical data designed to predict celestial events over an extended period from AH 89 to AH 689 (ca. 707–1307 CE), using the Hijra calendar. These tables primarily cover planetary positions for the five visible planets, as well as the Sun and Moon, alongside calculations for eclipses and planetary conjunctions. Their structure is organized into tables that facilitate step-by-step computations, enabling users to determine longitudes, latitudes, and other parameters with notable precision; for instance, the solar and lunar positions achieve errors typically less than 1° when compared to modern computations. The methodology employed in the Toledan Tables relies on a systematic division into tables, which track the average daily advances of celestial bodies along their orbits, and equation tables that apply corrections for eccentricities and anomalies using such as sines and tangents. corrections are integrated through dedicated tables that adjust for the gradual shift in the equinoxes, ensuring alignment with observational data from Toledo's . This computational approach builds on earlier zijes but introduces refined algorithms for iterative calculations, allowing for efficient manual computation without advanced instruments beyond basic astrolabes. Key innovations in the Toledan Tables include the explicit incorporation of apogee motion, accounting for the of the solar apogee—a refinement attributed to Al-Zarqali's observations—and the use of local parameters calibrated to Toledo's meridian, which is approximately 48°30' west of Baghdad's meridian. These elements bridge Ptolemaic geometric models with Indian arithmetic traditions, enhancing adaptability for diverse latitudes and marking a departure from the more rigid frameworks of predecessors like al-Battani's al-Sabi. However, the tables retain the geocentric model and do not fully reject the equant mechanism, limiting their departure from Ptolemaic orthodoxy and introducing inherent inaccuracies for certain planetary anomalies.

Major Works

Treatises on Instruments

Al-Zarqali authored several treatises dedicated to the construction and practical application of astronomical instruments, providing detailed instructions that advanced the instructional literature in Islamic astronomy. His Canon on the Use of the Astrolabe (known in Arabic as Al-Amal bi-l-Asturlab) serves as a comprehensive manual for operating the astrolabe, covering its projections, calibration techniques, and solutions to observational problems such as determining altitudes, azimuths, and time reckonings. This work emphasizes step-by-step procedures for users, integrating geometric constructions with practical examples to facilitate accurate measurements without relying on extensive tabular data. In his Book on the Composition of the Universal Plate (Kitab ma'rifat hadh al-a'ada al-kulliya, also referred to as a treatise on al-ṣafīḥa al-kullīya or plate), Al-Zarqali outlined methods for building and calibrating this innovative flat instrument, which allowed for computations across all latitudes through stereographic projections of celestial coordinates. The details the engraving of scales for the , , and horizons, along with instructions for aligning the plate to perform functions equivalent to a full spherical , such as solving spherical triangles and finding planetary positions. This work highlights the plate's portability and versatility, making it suitable for travelers and field astronomers. An original version is lost, but a Hebrew translation survives in the , preserving its core instructional content. Al-Zarqali also composed treatises on sundials, focusing on designs for both types, incorporating trigonometric scales to account for varying inclinations and orientations. These works describe the mathematical principles for laying out gnomons, hour lines, and arcs, enabling the construction of dials that accurately indicate and prayer times under different geographic conditions. Although the original Arabic on sundials is lost, its methods are referenced in later bibliographies and quotations by subsequent astronomers, such as those in the works of al-Marrakushi, underscoring its influence on dialling theory. Among his other contributions to instrumental literature, Al-Zarqali wrote a on the construction of the , preserved in an original manuscript at the , which provides guidance on assembling rings to model celestial motions for precise sightings. Additionally, his work on the equatorium, detailing the fabrication of a mechanical device for planetary position calculations via rotating diagrams, survives in a Hebrew held in the Sassoon collection in . These texts collectively emphasize hands-on fabrication and usage, distinguishing Al-Zarqali's approach by blending theoretical geometry with empirical adjustments derived from his observations in Toledo.

Tabular and Almanac Works

Al-Zarqali played a prominent role in the compilation of the Toledan Tables, a comprehensive set of astronomical tables completed around 1080, which incorporated adaptations from earlier works by al-Khwārizmī and al-Battānī while incorporating original mean-motion tables derived from observations at Toledo's coordinates. His contributions extended to the explanatory canon of these tables, particularly through the , which provided guidance on their usage for computing planetary longitudes and positions. This work drew on solar tables from Toledan observations and simplified calculations by employing Babylonian goal-year periods, facilitating practical applications in planetary almanacs. Al-Zarqali's tabular and almanac works circulated widely in the Islamic world in their original form and were later translated into Latin during the , notably by of , ensuring their transmission and use in medieval . The Almanach, in particular, survived in multiple versions, including an Alfonsine adaptation, underscoring its enduring practical value.

Legacy and Influence

Impact on Islamic Astronomy

Al-Zarqali's work profoundly shaped subsequent generations of Muslim astronomers, particularly through his mentorship and the dissemination of his theories on planetary motion. He directly influenced figures such as Ibn al-Kammad (d. 1115/16), who was educated in by Al-Zarqali's students and extended his predecessor's research on the motion of the solar apogee, incorporating it into his own tables like al-Muqtabas. Similarly, later astronomers including Abu al-Hasan al-Marrakushi (d. 1262) built upon Al-Zarqali's apogee model in their observational treatises, adapting his calculated rate of 12.04 arcseconds per year to refine solar theories in North African contexts. These connections highlight Al-Zarqali's role in fostering a tradition of empirical refinement within Andalusian and Maghrebi astronomy. The Toledan Tables, compiled under Al-Zarqali's leadership around 1080, saw widespread adoption across the Islamic world, extending from to and the eastern regions. In the Maghrib, these tables informed the zij works of astronomers like Ibn al-Banna (d. 1321) and were used for timekeeping and astrological computations well into the . Their methodology, blending Ptolemaic parameters with local observations, underscored the tables' utility in bridging western and eastern Islamic astronomical practices. Al-Zarqali's innovations in instrument design, notably the universal astrolabe known as the safiha zarqaliyya, proliferated through the School of Toledo and beyond, impacting later Islamic observatories. This flat, latitude-independent device facilitated accurate altazimuth measurements and was detailed in subsequent treatises, such as al-Marrakushi's 13th-century guide on its construction, which preserved and expanded Al-Zarqali's techniques for celestial observations. By the 14th and 15th centuries, variants of his designs appeared in and , aiding timekeeping and at institutions like the observatory, where they supported ongoing empirical studies. Medieval Arabic bibliographies consistently recognized Al-Zarqali as a pivotal innovator in , emphasizing his contributions to both theory and practice.

Transmission to

The transmission of Al-Zarqali's astronomical works to primarily occurred through the Toledo School of Translators in the , where Latin versions facilitated their integration into medieval . of , a prominent Italian scholar active in Toledo around 1175, produced Latin translations of key texts, including the Canones super tabulas Toletanas (a on the use of the Toledan Tables and astrolabes) and the Toledan Tables themselves, rendered as Tabulae Toletanae. These translations preserved Al-Zarqali's observational data on solar, lunar, and planetary motions, making them accessible to European astronomers who lacked direct access to sources. The Tabulae Toletanae exerted significant influence on subsequent European astronomical compilations, serving as a foundational reference until the mid-13th century. They informed the , commissioned by King in 1252 and completed around 1270, which adapted Al-Zarqali's parameters for Castilian latitudes while incorporating updated observations. This continuity is evident in the Alfonsine works' retention of Al-Zarqali's solar apogee motion—a motion of approximately 12.04 arcseconds per year relative to the —which marked a departure from Ptolemaic models and highlighted the oscillatory nature of planetary orbits. Later, 15th-century astronomers like ( Müller) drew upon the Toledan framework in his Tabulae directionum (printed 1512), using its trigonometric foundations for eclipse predictions and planetary positions. Al-Zarqali's ideas on apogee motion found direct citation in Nicolaus Copernicus's (1543), where Copernicus referenced the Toledan observations to support his heliocentric model's refinement of solar precession rates, attributing the discovery to "Arzachel" (the Latinized form of Al-Zarqali). This acknowledgment underscores Al-Zarqali's role in challenging static Ptolemaic astronomy and paving the way for innovations. Additionally, his trigonometric methods, including tables of sines, tangents, and chords derived from observations, extended beyond tabular computations to underpin treatises on , such as those by , enabling more accurate spherical projections and navigational reckonings. Al-Zarqali's instrumental innovations, particularly the safiha (a universal flat or "azafea"), were transmitted via Alfonso X's Libros del saber de astronomía (1276–1279), which included Romance translations of his treatises. Known in as the Saphea Arzachelis, this device allowed latitude-independent measurements of altitudes and azimuths, proving invaluable for medieval during the Age of Exploration; it remained in use by mariners and surveyors into the , influencing designs in Portuguese and Spanish shipboard astronomy. Its planar projection also informed early mechanical clocks, where geared mechanisms mimicked the safiha's rotational dials for timekeeping aligned with celestial events, bridging astronomical and horology until superseded by more precise instruments like Tycho Brahe's quadrants.
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