He made observations from 825 to 835, and compiled three astronomical tables: the first were still in the Hindu manner; the second, called the 'tested" tables, were the most important; they are likely identical with the "Ma'munic" or "Arabic" tables and may be a collective work of al-Ma'mun's astronomers; the third, called tables of the Shah, were smaller.
Apropos of the solar eclipse of 829, Habash gives us the first instance of a determination of time by an altitude (in this case, of the sun); a method which was generally adopted by Muslim astronomers.
In 830, he seems to have introduced the notion of "shadow", umbra (versa), equivalent to our tangent in trigonometry, and he compiled a table of such shadows which seems to be the earliest of its kind. He also introduced the cotangent, and produced the first tables of for it.
The Book of Bodies and Distances
Al-Hasib conducted various observations at the Al-Shammisiyyah observatory in Baghdad and estimated a number of geographic and astronomical values. He compiled his results in The Book of Bodies and Distances, in which some of his results included the following:
^General Cartography : "The Iranian geographers Abū Muhammad al-Hasan al-Hamdānī and Habash al-Hasib al-Marwazi set the Prime Meridian of their maps at Ujjain, a center of Indian astronomy"
^ : "Additionally in the ninth century, the Persian mathematician and geographer, Habash al-Hasib al-Marwazi, utilized the utilization circular trigonometry and guide projection strategies keeping in mind the end goal to change over polar directions to an alternate arrange framework fixated on a particular point on the circle, in this the Qibla, the course to Mecca. Abū Rayhān Bīrūnī (973– 1048) later created thoughts which are viewed as a reckoning of the polar organize framework."