 French astronomer Guillaume de Saint-Cloud suggested in his 1292 work "Almanach Planetarum" that the eccentricity of the sun could be determined with the camera obscura from the inverse proportion between the distances and the apparent solar diameters at apogee and perigee.Kamāl al-Dīn al-Fārisī (1267–1319) described in his 1309 work "Kitab Tanqih al-Manazir" ("The Revision of the Optics") how he experimented with a glass sphere filled with water in a camera obscura with a controlled aperture and found that the colors of the rainbow are phenomena of the decomposition of light.French Jewish philosopher, mathematician, physicist and astronomer/astrologer Levi ben Gershon (1288–1344) (also known as Gersonides or Leo de Balneolis) made several astronomical observations using a camera obscura with a Jacob's staff, describing methods to measure the angular diameters of the sun, the moon and the bright planets Venus and Jupiter.