Li Fan (Chinese: 李梵; pinyin: Lǐ Fàn) was a Chinese astronomer during the Han dynasty (202 BC – 220 AD).
He noticed that the Moon does not move uniformly through its phases by using background stars as reference.[citation needed] In 85 Li Fan and Bian Xin (Chinese: 編訢) were tasked by Emperor Zhang to resolve inaccuracies in the Taichu calendar.[1][2] He is also known to have worked with inflow clepsydras as opposed to earlier, typically less accurate outflow clepsydras.[3]
The measurements of synodic periods of the planets given in the following table are attributed to him.[4]
| Planet | True value (days) | Li Fan's value (days) |
|---|---|---|
| Mercury | 115.877 | 115.881 |
| Venus | 583.921 | 584.024 |
| Mars | 779.936 | 779.532 |
| Jupiter | 398.884 | 398.846 |
| Saturn | 378.092 | 378.059 |
An impact crater that is located at the Phaethontis quadrangle, Mars, 47.2°S Latitude and 153.2°W Longitude was named in his honor. The diameter of the impact crater is approximately 104.8 km.