One of al-Battani's greatest contributions was his introduction of the use of sines and tangents in geometrical calculations, especially spherical trigonometric functions, to replace Ptolemy's geometrical methods. Al-Battānī's methods involved some of the most complex mathematics developed up to that time. He was aware of the superiority of trigonometry over geometrical chords, and demonstrated awareness of a relation between the sides and angles of a spherical triangle, now given by the expression:

${\displaystyle \cos a=\cos b\cos c+\sin b\sin c\cos A}$

Al-Battānī produced a number of trigonometrical relationships:

${\displaystyle \tan \alpha ={\frac {\sin \alpha }{\cos \alpha }}}$

${\displaystyle \sec \alpha ={\sqrt {1+\tan ^{2}\alpha }}}$, where ${\displaystyle \sec \alpha ={\frac {1}{\cos \alpha }}}$.

He also solved the equation

${\displaystyle \sin x=y\cos x}$,

discovering the formula

${\displaystyle \sin x={\frac {y}{\sqrt {1+y^{2}}}}}$

Al-Battānī used the Iranian astronomer Habash al-Hasib al-Marwazi's idea of tangents to develop equations for calculating and compiling tables of both tangents and cotangents. He discovered their reciprocal functions, the secant and cosecant, and produced the first table of cosecants for each degree from 1° to 90°, which he referred to as a "table of shadows", in reference to the shadow produced on a sundial.

Using these trigonometrical relationships, al-Battānī created an equation for finding the qibla, which Muslims face in each of the five prayers they practice every day. The equation he created did not give accurate directions, as it did not take into account the fact that Earth is a sphere. The relationship he used was precise enough only for a person located in (or close to) Mecca, but was still a widely used method at the time. Al-Battānī's equation for ${\displaystyle q}$, the angle of the direction of a place towards Mecca is given by:

${\displaystyle \tan q={\frac {\sin \Delta \lambda }{\sin \Delta \phi }}}$

where ${\displaystyle \Delta \lambda }$ is the difference between the longitude of the place and Mecca, and ${\displaystyle \Delta \phi }$ is the difference between the latitude of the place and Mecca.

Al-Battānī's equation was superseded a century after it was first used, when the polymath al-Biruni summarized several other methods to produce results that were more accurate than those that could be obtained using al-Battānī's equation.

A small work on trigonometry, Tajrīd uṣūl tarkīb al-juyūb ("Summary of the principles for establishing sines") is known. Once attributed to the Iranian astronomer Kushyar Gilani by the German orientalist Carl Brockelmann, it is a fragment of al-Battānī's zīj. The manuscript is extant in Istanbul as MS Carullah 1499/3. The authenticity of this work has been questioned, as scholars believe al-Battānī would have not have included al-juyūb for "sines" in the title.

Al-Battānī's Kitāb az-Zīj (كتاب الزيج or زيج البتاني, "Book of Astronomical Tables"), written in around 900, and also known as the al-Zīj al-Ṣābī (كتاب الزيج الصابئ), is the earliest extant zīj made in the Ptolemaic tradition that is hardly influenced by Hindu or Sasanian–Iranian astronomy. It corrected mistakes made by Ptolemy and described instruments such as horizontal and vertical sundials, the triquetrum, the mural instrument, and a quadrant instrument. Ibn al-Nadim wrote that al-Battānī's zīj existed in two different editions, "the second being better than the first". In the west, the work was sometimes called the Sabean Tables.

The work, consisting of 57 chapters and additional tables, is extant (in the manuscript árabe 908, held in El Escorial), copied in Al-Andalus during the 12th or 13th century. Incomplete copies exist in other western European libraries. Much of the book consists of instructions for using the attached tables. Al-Battānī used an Arabic translation of the Almagest made from Syriac, and used few foreign terms. He copied some data directly from Ptolemy's Handy Tables, but also produced his own. His star table of 880 used around half the stars found in the then 743-year-old Almagest. It was made by increasing Ptolemy's stellar longitudes, to allow for the different positions of the stars, now known to be caused by precession.

Other zījes based on Kitāb az-Zīj aṣ-Ṣābi’ include those written by Kushyar Gilani, Alī ibn Ahmad al-Nasawī, Abū Rashīd Dāneshī, and Ibn al-Kammad.

The first version in Latin from the Arabic was made by the English astronomer Robert of Ketton; this version is now lost. A Latin edition was also produced by the Italian astronomer Plato Tiburtinus between 1134 and 1138. Medieval astronomers became quite familiar with al-Battānī through this translation, renamed De motu stellarum ("On stellar motion"). It was also translated from Arabic into Spanish during the 13th century, under the orders of Alphonso X of Castile; a part of the manuscript is extant.

The zīj appears to have been widely used until the early 12th century. One 11th-century zīj, now lost, was compiled by al-Nasawī. That it was based on al-Battānī can be inferred from the matching values for the longitudes of the solar and planetary apogees. Al-Nasawī had as a young man written astronomical tables using data obtained from al-Battānī's zīj, but then discovered the data he used had been superseded by more accurately made calculations.

The invention of movable type in 1436 made it possible for astronomical works to be circulated more widely, and a Latin translation of the Kitāb az-Zīj aṣ-Ṣābi’ was printed in Nuremberg in 1537 by the astronomer Regiomontanus, which enabled Al-Battānī's observations to become accessible at the start of the scientific revolution in astronomy. The zīj was reprinted in Bologna in 1645; the original document is preserved at the Vatican Library in Rome.

The Latin translations, including the printed edition of 1537, made the zīj influential in the development of European astronomy. A chapter of the Ṣābiʾ Zīj also appeared as a separate work, Kitāb Taḥqīq aqdār al-ittiṣālāt [bi-ḥasab ʿurūḍ al-kawākib] ("On the accurate determination of the quantities of conjunctions [according to the latitudes of the planets]").

Al-Battānī's work was published in three volumes, in 1899, 1903, and 1907, by the Italian Orientalist Carlo Alfonso Nallino, who gave it the title Al-Battānī sive Albatenii opus astronomicum: ad fidem codicis Escurialensis Arabice editum. Nallino's edition, although in Latin, is the foundation of the modern study of medieval Islamic astronomy.

Kitāb maʿrifat maṭāliʿ al-burūd̲j̲ fī mā baina arbāʿ al-falak (معرفة مطالع البروج, “The book of the science of the ascensions of the signs of the zodiac in the spaces between the quadrants of the celestial sphere”) may have been about calculations relating to the zodiac. The work is mentioned in a work by Ibn al-Nadim, and is probably identical with chapter 55 of al-Battānī's zīj. It provided methods of calculation needed in the astrological problem of finding al-tasyīr (directio).

• Kitāb fī dalāʾil al-qirānāt wa-l-kushūfāt ("On the astrological indications of conjunctions and eclipses") is a treatise on horoscopes and astrology in connection with conjunctions of Saturn and Jupiter that occurred during the earliest period of Islam. The extant manuscript is held in the İsmail Saib Library at Ankara University.
• Sharḥ kitāb al-arbaʿa li-Baṭlamiyūs (شرح كتاب الأربع مقالات في أحكام علم النجوم, "Commentary on Ptolemy's Tetrabiblos") is a commentary on the Kitāb al-Arbaʿ maqālāt in the version of Abu as-Salt. Al-Battānī mentions two earlier treatises that are likely identical to two chapters of the Ṣābiʾ Zīj. It is extant in the manuscripts Berlin Spr. 1840 (Ahlwardt #5875) and Escorial árabe 969/2.
• Arbaʻ maqālāt (أربع مقالات, "Four discourses") was a commentary on Ptolemy's Quadripartitum de apotelesmatibus e judiciis astrorum, known as the Tetrabiblos. The 10th-century encyclopedist Ibn Nadim in his Kitāb al-Fihrist, lists al-Battānī among a number of authors of commentaries on this work.
• Maʻrifat maṭāliʻ al-burūj (معرفة مطالع البروج, "Knowledge of the rising-places of the zodiacal signs").
• Kitāb fī miqdār al-ittiṣālāt (كتاب في مقدار الاتصالات), an astrological treatise on the four "quarters of the sphere".

The al-Zīj al-Ṣābī was renowned by medieval Islamic astronomers; the Arab polymath al-Bīrūnī wrote Jalā' al-adhhān fī zīj al-Battānī ("Elucidation of genius in al-Battānī's Zīj"), now lost.

Al-Battānī's work was instrumental in the development of science and astronomy in the west. Once it became known, it was used by medieval European astronomers and during the Renaissance. He influenced Jewish rabbis and philosophers such as Abraham ibn Ezra and Gersonides. The 12th-century scholar Moses Maimonides, the intellectual leader of medieval Judaism, closely followed al-Battānī. Hebrew editions of the al-Zīj al-Ṣābī were produced by the 12th-century Catalan astronomer Abraham bar Hiyya and the 14th-century French mathematician Immanuel Bonfils.

Copernicus referred to "al-Battani the Harranite" when discussing the orbits of Mercury and Venus. He compared to his own value for the sidereal year with those obtained by al-Battānī, Ptolemy and a value he attributed to the 9th-century scholar Thabit ibn Qurra. The accuracy of al-Battānī's observations encouraged Copernicus to pursue his ideas about the heliocentric nature of the cosmos, and in the book that initiated the Copernican Revolution, the De Revolutionibus Orbium Coelestium, al-Battānī is mentioned 23 times.

Al-Battānī's tables were used by the German mathematician Christopher Clavius in reforming the Julian calendar, leading to it being replaced by the Gregorian calendar in 1582. The astronomers Tycho Brahe, Giovanni Battista Riccioli, Johannes Kepler and Galileo Galilei cited Al-Battānī or his observations. His almost exactly correct value obtained for the Sun's eccentricity is better than the values determined by both Copernicus and Brahe.

The lunar crater Albategnius was named in his honour during the 17th century. Like many of the craters on the Moon's near side, it was given its name by Riccioli, whose 1651 nomenclature system has become standardized.

In the 1690s, the English physicist and astronomer Edmund Halley, using Plato Tiburtius's translation of al-Battānī's zīj, discovered that the Moon's speed was possibly increasing. Halley researched the location of Raqqa, where al-Battānī's observatory had been built, using the astronomer's calculations for the solar obliquity, the interval between successive autumnal equinoxes and several solar and lunar eclipses seen from Raqqa and Antioch. From this information, Halley derived the mean motion and position of the Moon for the years 881, 882, 883, 891, and 901. To interpret his results, Halley was dependent upon on knowing the location of Raqqa, which he was able to do once he had corrected the accepted value for the latitude of Aleppo.

Al-Battānī's observations of eclipses were used by the English astronomer Richard Dunthorne to determine a value for the increasing speed of the Moon in its orbit, he calculated that the lunar longitude was changing at a rate of 10 arcseconds per century.

Al-Battānī's data is still used by geophysicists.

• List of Arab scientists and scholars

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• c. 1245–1250 – Gerard of Abbeville Manuscript: Latin 16657 (Liber Albategni. – Almagesti minoris libri VI. – Tabule stellarum fixarum)
• 1376–1475 – Manuscript:Vat.lat.3098 (De Scientia stellarum (opus astronomicum) – Interpretatio latina Platonis Tiburtini. Praeit interpretis praefatio)
• 14th century – Manuscript Latin 7266 (Opusculum cujus titulus : liber Machometi, filii Gebir, filii Cinem, qui vocatur Albateni, in numeris stellarum et in locis motuum earum, experimenti ratione conceptorum : interprete Platone Tiburtino)

• Battani (al-), Muḥammad ibn Jabir (1899). Nallino, Carlo Alfonso (ed.). Al-Battānī sive Albatenii opus astronomicum: ad fidem codicis Escurialensis Arabice editum (Kitāb Zīj al-Ṣābī') (in Arabic). Vol. 3. Milan: Mediolani Insubrum: Prostat apud Urlichum Hoeplium. ISBN 978-88-88097-26-8.
• Battani (al-), Muḥammad ibn Jabir (1903). Nallino, Carlo Alfonso (ed.). Al-Battānī sive Albatenii opus astronomicum: ad fidem codicis Escurialensis Arabice editum (Kitāb Zīj al-Ṣābī') (in Arabic). Vol. 1. Milan: Mediolani Insubrum: Prostat apud Urlichum Hoeplium. ISBN 978-88-88097-26-8.
• Battani (al-), Muḥammad ibn Jabir (1907). Nallino, Carlo Alfonso (ed.). Al-Battānī sive Albatenii opus astronomicum: ad fidem codicis Escurialensis Arabice editum (Kitāb Zīj al-Ṣābī') (in Arabic). Vol. 2. Milan: Mediolani Insubrum: Prostat apud Urlichum Hoeplium. ISBN 978-88-88097-26-8.

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• Sarton, George (1960). A History of Science: Ancient Science Through the Golden Age of Greece. Vol. 1. Cambridge, Massachusetts: Harvard University Press. OCLC 179869164.