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Understanding and Observing the Moon's Phases and Eclipses

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Understanding and Observing the Moon's Phases and Eclipses Because of the Moon’s trek around the sky, from time to time it passes near or even Understanding drifts over other celestial objects. Close approaches are known as conjunctions , whereas covering another object is called an occultation and Observing or eclipse, depending on whether a night time object or the Sun is covered. Tight groupings of the Moon with bright planets or stars are striking sights and make excellent photographs, particularly if a scenic The Moon, earthly foreground is included. Use a camera tripod to make sure your camera stays steady during the time exposure. Depending on your choice of camera, exposures of about ¼ its Phases to a few seconds should give useable results. Don’t forget to experiment with subtle foreground lighting for dramatic effects. and Lunar Phases Eclipses A common misconception is that lunar phases are somehow caused by the shadow of the Earth falling onto the Moon. In The Moon is Earth’s closest companion in reality, the Moon’s phases are the result of space. Though well studied, to many people, our changing viewing angle of the Moon as it Earth’s rocky ‘sibling’ represents an orbits the Earth. unknown entity. This brochure will become apparent in the evening sky shortly About 7 days after New Moon, the shadow introduce you to lunar phases and motions Understanding the Moon’s phases cannot after sunset. Because the Moon is now line separating the lit as well as explain the basics of eclipses. really be done without also understanding surrounded by darker sky, the faintly and unlit portions of how the Moon’s position in the sky varies luminous shaded part of the Moon (known as Lunar Motions throughout the lunar month. the Moon is now visible the terminator) is due to earth shine, the straight. This represents The Moon is a cold, rocky body 3,476 km A New Moon occurs when the Moon lies reflected light from a the First Quarter Moon across and can easily fit between Vancouver hidden in the Sun’s glare and not visible nearly fully-illuminated because we are now and Ottawa. It has no light of its own but because only the shaded side is facing us. Earth (as seen from the one quarter through the Moon’s orbit shines by sunlight reflected from its surface. Over a few days, a thin waxing crescent will Moon). This stage is commonly described as around the Earth. This Lunar phase is the ‘old Moon in the new Moon’s arms.’ visible throughout the afternoon in a bright daylight sky. Even though the Moon is high to complete this cycle; one lunar month has Eclipses Summary in the south at sunset, and in dark skies passed. In fact, this is the origin of the word during the evening, Earth shine on the ‘month.’ There is a time that the Earth’s shadow can The Moon presents an ever-changing face to shaded part of the Moon is difficult to see, change the Moon’s appearance, and that is us because of its movement through our day since the Earth, as seen from the Moon, is Named Moons during a lunar eclipse, when the Moon passes and night skies and is an ideal way for a also only half illuminated and not as bright as through the Earth’s shadow. A Lunar beginner to enjoy astronomy as well as for earlier in the cycle. In binoculars and small A number of full Eclipse only occurs during a Full Moon, experts to ponder its movements and origin. telescopes, craters are easily visible along the Moons in a given year though not all Full Moons produce an terminator. have widely recognised eclipse because the Moon’s orbit is oblique More information on the topics covered in names Honey, Hunter, to the Earth’s orbit around the Sun. An this brochure is available in the Observer’s Two weeks after New Moon, the Moon is Harvest, but all Full eclipse can only occur when the Moon is Handbook , which is included with Full and rises as the Sun sets and sets when Moons are named, crossing the Earth’s orbital plane and the membership in the Royal Astronomical the Sun rises. In other words, it is visible albeit with sometimes Moon, Earth and Sun are lined up. For Society of Canada. only in a darkened sky. lesser-known monikers. more information, see our companion An astronaut on the brochure, Observing and Understanding Lunar Find out more Moon would now see a January - Wolf, Hunger, Old Eclipses. ‘New Earth’, completely February - Snow, Ice To learn more about the Royal Astronomical in shadow. Now the March - Worm, Sap, Sugaring, Crow, Storm A related phenomenon is the solar eclipse Society of Canada, or membership in the craters are only seen April - Pink, Egg, Gras, Rai, Growing when the Sun is covered because the Moon Society, contact your local Centre or the with difficulty, but May - Flower, Planting, Milk, Hare is passing between the Sun and the Earth. Society’s National Office: surface brightness June - Strawberry, Rose, Honey, Mead This event takes place only on select New variationss are best seen. Darker maria July - Buck, Thunder, Deer, Hay Moons. Website: (pronounced mar’ ee uh, Latin for seas) August - Sturgeon, Corn, Fruit, Barley www.rasc.ca September - Harvest (nearest autumn equinox) Tides stand out from lighter highlands and both are dusted by bright white rays of material October - Hunter's (after Harvest) E-mail: November - Beaver, Frost, Snow spewed from younger craters. The tides on the Earth are primarily due to [email protected] December - Cold, Long Night, Winter the change in intensity of the Moon's A Third or Last Quarter Moon is seen in gravitational pull from one side of the Earth Telephone: dark skies only in the ‘Once in a blue moon’ is used to refer to a to the other. This forms two tidal bulges, Phone: (416) 924-7973 predawn and sets in the rare event, four Full Moons in a season. one on either side of the Earth. Fax: (416) 924-2911 west at about noon. However, due to a mistake made in an The Moon’s phase astronomy magazine in the late 1940’s, Full Moon Effect Mailing Address: continues to wane and popular culture has embraced a revised The Royal Astronomical Society of Canada Earth shine is again definition: the blue moon is the second Full Some people blame the Moon for affecting 203 - 4920 Dundas St W obvious just before Moon in the same month. Both occur with people’s moods, but careful scientific studies Toronto ON M9A 1B7 sunrise where we see the ‘new Moon in old roughly equal frequency; about one every over the years have found no measurable Moon’s arms.’ It takes the Moon 29.5 days two and a half years. effect. .
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