Waxing crescent Moon. Image 1 of 15. Optical image of a waxing (increasing in apparent size) crescent Moon three days into its 28-day cycle. The phases of the Moon are due to it revealing different amounts of its sunlit face as it orbits the Earth. The grey circular area at upper right is the lunar sea called Mare Crisium. Image taken on 5th June 2000. For a sequence showing the Moon throughout its cycle of phases, see images R340/596-610.