| In astronomy he worked on making observations more precise by improving astronomical instruments. |
| By 1905, of course, astronomical observations had greatly improved due to photography. |
| Galileo wrote to astronomers in other cities and compared their observations with his own. |
| This division carries out aerological observations at the internationally specified times everyday. |
| Al-Mahri used astronomical observations of the height of stars to determine the difference in latitude between two places. |
| He began correcting the errors in existing astronomical tables by making observations of the motion of the planets with a cheap telescope. |
