Obviously, the geometry of the Moon's path through the umbra plays an important role. The Moon's appearance can vary enormously throughout the period of totality and from one eclipse to the next. The total lunar eclipse is the most dramatic and visually compelling type of lunar eclipse. Whether the Moon was high in the sky or low near the horizon.Īristotle correctly reasoned that only a sphere casts a round shadow from every angle. In comparing observations of several eclipses, he noted that Earth's shadow was round no matter where the eclipse took place, May be brighter by a factor of about 500x.īecause the umbral shadow's diameter is typically ˜2.7x the Moon's diameter, it appears as thoughĪ semi-circular bite has been taken out of the Moon.Īristotle (384-322 BCE) first proved that Earth was round using the curved umbral shadow seen at partial eclipses. This is primarily due to a contrast effect because the remaining portion of the Moon in the penumbra ![]() The lunar limb extending into the umbral shadow usually appears very dark or black. In comparison, partial eclipses are easy to see with the naked eye. The penumbral eclipse only becomes readily apparent when it is within ˜0.05 magnitudes of becoming a partial eclipse. Under such conditions, the Moon remains relatively bright with only a subtle gradient across its disk. Invisible to the eye with or without optical aid.Ī penumbral magnitude greater than ˜0.6 is needed before skilled observers can detect faint shading across the Moon's disk.Įven when one edge of the Moon is 9/10 of the way into the penumbral shadow, approximately 10% of the Sun's rays still The primary penumbral contacts (P1 and P4), as well as the early and late stages of a penumbral eclipse, are completely Thus, some fraction of the Sun's direct rays continues to reach the most deeply eclipsed parts of Appearance of Penumbral and Partial Lunar EclipsesĮarth's penumbral shadow forms a diverging cone that expands into space in the anti-solar direction.įrom within this zone, Earth blocks part but not the entire disk of the Sun. ![]() While total eclipses are colorful and dramatic. While penumbral eclipses are pale and difficult to see, partial eclipses are easy naked-eye events, The visual appearance of penumbral, partial, and total lunar eclipses differs significantly from each other. Visual Appearance of Lunar Eclipses Five Millennium Canon of Lunar Eclipses Introduction
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