page_title: Lunar limb
hierarchical_section_title: Lunar limb
caption_attribution_description: English: Earthshine reflecting of the Moon. Photo taken in Longjing Township,Taichung County,Taiwan on 13 September 2010, 18:39 (UTC+8) by 阿爾特斯.At that time the moon was moving nearby Libra. 中文（繁體）‎: 地照反射月球，這張照片拍攝於2010年9月13日18:39分的台灣台中縣龍井鄉地區，當時月球正運行在天秤座附近。
context_page_description: The lunar limb is the edge of the visible surface of the Moon as viewed from Earth. Libration of the Moon, with its irregular surface, leads to small changes in its profile; this complicates the task of precisely calculating eclipse times and durations. However, data from the mapping of the lunar surface allows astronomers to predict the lunar profile for any given time with a high degree of certainty. The irregularity of the lunar limb is the cause of Baily's beads, which are collimated rays of sunlight that shine through in some places while not in others during a solar eclipse.
  The contrast of the lunar disc, brightly illuminated by direct sunlight, against a black night sky makes it a popular target when testing telescope optics.
context_section_description: The lunar limb is the edge of the visible surface (disc) of the Moon as viewed from Earth. Libration of the Moon, with its irregular surface, leads to small changes in its profile; this complicates the task of precisely calculating eclipse times and durations. However, data from the mapping of the lunar surface allows astronomers to predict the lunar profile for any given time with a high degree of certainty. The irregularity of the lunar limb is the cause of Baily's beads, which are collimated rays of sunlight that shine through in some places while not in others during a solar eclipse.
  The contrast of the lunar disc, brightly illuminated by direct sunlight, against a black night sky makes it a popular target when testing telescope (including binocular) optics.
caption: Two contrasting lightnesses of the lunar disc at crescent phase, overexposed to show earthshine
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