04ch4Observing2

04ch4Observing2 - Chapter 4: Motions and Time Constellation...

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1 Chapter 4: Motions and Time Constellation Cygnus Moons phases and eclipses Motion of Moon, Earth and Sun Paths in the sky: rising, setting, seasons Time and calendars
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2 Constellation Cygnus Right Ascension: 21 hours Declination: 40 degrees Visible from latitudes 90 to -40 degrees Best seen in September (at 9:00 PM) The Milky Way passes through Cygnus Star Deneb is 18 th brightest in sky
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3 Phases of the Moon view from Earth (side facing moon) view from space 2 Qs: Where sun. . Stood on moon
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4 Where to find the Moon in the Sky The phase of the moon is a measure of the angle between the Sun and the Moon seen from Earth. New moon is in the direction of the sun. Rises and sets about same time as sun. A crescent Moon is farther from sun than the new moon but still near the Sun first or last quarter (half Moon) must be overhead when the Sun is rising or setting full Moon rises when the Sun sets, and it is highest in the sky near midnight. 3Qs: highest in sky. . rise…set? North pole
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5 Lunar Eclipses: Sun-Earth-Moon in line A lunar eclipse occurs when the Moon is in the Earth’s shadow. sees the eclipse. It looks sunlight is refracted (bent) through our atmosphere . The Moon must be full.
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6 Solar Eclipses: Sun-Moon-Earth in line Solar eclipses happen when the Moon passes between us and the Sun. The Moon must be new. 3Qs: type . .type. . and phase
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7 Eclipses and shadows The Moon happens to have about the same angular size as the Sun. The moon can just completely cover the sun when perfectly aligned. The type of solar eclipse (total, partial, annular) depends on Earth’s position in Moon’s shadow. Memorize!
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8 Total Solar Eclipses The sky dark, stars visible. Lasts few minutes in any one place. Somewhere on Earth: 1 or 2 per year. Q: solar eclipse. . A total (solar) eclipse: sun-moon-Earth in exact alignment.
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9 The Path of totality moves The Moon’s orbit carries the path of totality across the spinning Earth. You will see a total eclipse from the blue regions. From a specific place: centuries between total eclipses movie: www.moonglow.net /eclipse/
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10 Eclipses are not bi-weekly Moon’s orbit is tilted 5 degrees to the Earth-sun line Earth and moon are far apart. Accurate scale Moon shown too near and too big
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11 The Sky Because the Earth is a sphere, the positions of the stars in your sky, and those at your zenith and horizon depend on where you are on Earth. somewhere on the equator. Different stars are at the Zenith of each. You see at most ½ the sky at one time.
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12 Diurnal (daily) Motion from N Pole and Equator The horizons, shown as white lines in previous slide, are now shown as the large inclined circles.
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13 The Celestial Sphere Celestial sphere is imaginary sphere centered on the Earth.
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This note was uploaded on 02/17/2009 for the course PHYS 7 taught by Professor Staff during the Winter '08 term at UCSD.

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04ch4Observing2 - Chapter 4: Motions and Time Constellation...

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