Astronomer and mathematician (B. 770, Merv /
Resources mention that Habeş, one of the first Muslim astronomers and mathematicians, followed the Indian mathematics and astronomy model in the beginning of his scientific life and based his first “zîcde” (map of stars) on the Sindhind (Siddhanta) tradition. Although it is not certain whether it was actually in the astronomy observers group protected by the Khalif Me’mûn, it is understood from his “ez-Zîcü’l-Mümtehan” that he followed their works closely and tested their conclusions together with his own observations. In this work and his later works, Habeş proved that he knew about Greek astronomy, as well as Indian astronomy. Although he went beyond that, he arranged his maps according to the Ptolemy model. It is understood that his research had a strong influence on his later colleagues.
Ahmed b. Abdullah
el-Mervezî el-Bağdadî was one of the important figures of the early Islam
astronomy and trigonometry. The first to mention his name, İbn Nedîm (D. 990), talked
about him in “el-Fihrist” as one of
the first observers. Another resource mentioning Habeş, İbn el-Kıftî (D. 1248/1249),
said in his “İhbâr el-Ulemâ bi-Ahbâr
el-Hukemâ” that Habeş’ nickname was Habeş el-Hâsib. As İbn Nedîm did, he
reported that he had been from Merv (in
Ebü’l-Hasan İbn Yûnus, through whom we
know that Habeş performed observations in
The most striking achievement of Habeş can be seen in his application of trigonometric functions to the problems of the global astronomy. In these efforts, following Hârizmî, the first to come up with the sine chart (ceyb meb-sût) in the Islam trigonometry history, he prepared the sine charts for the values 0 = 0: 0°, 0; 15°, 0; 30°, 0; 45°, 1; 0°... 90: 0°, and, to separate sine and “versine”, he used the term “ceyb ma’kûs” for the first time. Furthermore, it can be seen that he went beyond Hârizmî, who had used the term “ceyb menkûs” for “versine”, and he clarified the distinction between these terms.
Habeş el-Hâsib found a new method to estimate time by observing the raise of the sun, and this method was also used by later astronomers. According to this method, at dawn, the sun was on the skyline, with 0 heights, only to increase later on. It was at its peak at noon time and its height gradually decreases, only to disappear at the vanishing point. Therefore, height of the sun gave us the time passed. In his work “Devâir el-Sumut fi el-Usturlab”, Ebu Nasr Mansur b. el-Iraki examined Habeş el-Hâsib’s two original methods about the indication of the azimuth circles on the astrolabe. The “geometrical proposition” Habeş used in this was quite interesting and his method was not used in the later literature.
ez-Zîc alâ mezhebi's-Sindhind, ez-Zîcü'l-müm-tehan, ez-Zîcü'd-Dımaşki. (Sâlih Zeki claimed it was the same work as ez-Zîcü'l-mümte-han.), ez-Zîcü’ş-şağir (also known with the name Zîcü’ş-şâh, could not survive till today), ez-Zîcü’l-Me’mûnî (Sâlih Zeki claimed this work, which could not survive till today, was the same work as ez-Zîcü’l-mümtehan, like ez-Zîcü’d-Dımaşki), Kitâbü Ameli’I-usturlâb, Kitâb fî ma rifeti’l-küre ve’l-‘amel bihâ (About the definition of the sphere and its usage in astronomical observations), Ma’rifetü keyfiyyeti’l-erşâd ve’l-amel bizâti’l-halak (Describes how the astronomy device called “Zâtü’l-halak” should be used).
Besides these, works such as Kitâbü’l-Eb'âd ve’l-ecrâm, Kitâbü’d-Devâ’iri’ş-şelâşi’l-mü-mâsse and keyfiyyeti’l-evşâl, Kitâbü’r-Rahâ im ve’l-makayîs, Kitâbü ‘Ameli’s-sutûhi’l-mebsûta ve’l-ka ime ve’l-mâ and ve’l-münharife are said to have existed, in various sources.