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Astro*Dictionary by Michael Erlewine





1 article for "Visibility"

Visibility [DeVore]

Moon. As the New Moon begins to separate from its conjunction with the Sun, it becomes visible in the West just after Sunset. Each successive evening it is higher in the sky, hence sheds its light for nearly an hour longer before it sets. A first quarter Moon is always seen directly overhead immediately after sunset. At the Full Moon the Sun's setting reveals the Moon just rising in the East, hence the Full Moon shines throughout the entire night. As each night it rises an hour later, by the time it reaches its last quarter it does not rise until midnight, and is overhead when the morning Sun, rising in the East, blots it from view. At the next Lunation the Moon traverses the sky along with the Sun, and is invisible - except as it eclipses the Sun, when it shows as a dark shadow crossing the Sun. A day later it reappears in the West, just after the fading light of the Sun renders it visible. Mercury. Its periods of visibility follow a pattern similar to that of the Moon, in a cycle of from 3½ and 4½ months. A few days after its inferior conjunction it fades into view in the West about an hour after sunset. Each night for about three nights it climbs higher in the western sky to its point of greatest elongation; then falls back until it disappears. Five to six weeks later, in the middle of its retrograde period, occurs its superior conjunction, when its rays are completely enveloped by those of the Sun. In another five or six weeks it attains to a sufficient elongation to become visible in the East just before Sunrise. Each of three mornings finds it a little higher in the sky, after which it as quickly recedes — and another cycle begins. Venus. Its cycle is strikingly similar to that of the Moon-including its phases; but while Mercury makes its superior conjunction approxi- mately every four months at an advance of four Signs, the Venus superior conjunction occurs every two years, approximately, at an advance of nine signs. Mars, Jupiter and Saturn. Similarly the major planets depend for visibility upon their positions relative to the Sun, whereby the planet can be above the horizon at a time when the Sun is below it. A study of the phenomena of visibility of a planet with regards to the relative positions of the Sun and Moon, will contribute to a better understanding of the Doctrine of Orientality, which decrees that a planet is more advantageously placed when oriental of the Sun, and occidental of the Moon.

Mercury was an Evening Star in November of 1943-1944, and will be on every sixth year thereafter; 1949-1950, and so on.

Venus was an Evening Star in November 1941, 1944, 1946 and 1947, and will be on every eighth year after each of these dates.

Mars was a Morning Star in 1947, and will be every second year thereafter for many years.

Jupiter is visible in the evening during 1947-1951.

Saturn will be a Morning Star for several years from 1945.

The major planets are brightest when in opposition to the Sun, when they are visible throughout the entire night.

Uranus is sometimes visible to the unaided eye on a Moonless night, when it is in a near conjunction with Mars.

Neptune and Pluto are never visible except with the aid of a telescope.

See also:
♦ Astronomy ♦ Brightness


Astro*Index Copyright © 1997 Michael Erlewine