You Know Astronomy!You Know Astronomy!

Observing the motions of Sun, Moon, Observing the motions of Sun, Moon, StarsStars

Observing the appearance of the Sun, Observing the appearance of the Sun, Moon, StarsMoon, Stars

Observing the passage of timeObserving the passage of time

Celestial MotionsCelestial Motions

Sun, Moon and Stars appear to rise in the Sun, Moon and Stars appear to rise in the East and set in the West dailyEast and set in the West daily

Actual motion is the rotation of the Earth Actual motion is the rotation of the Earth from West toward East dailyfrom West toward East daily

Solar Day-Noon to NoonSolar Day-Noon to NoonTime ZonesTime Zones

SEASONSSEASONS

Why do we have seasons?Why do we have seasons?

The AnswerThe Answer

The Earth is The Earth is TiltedTilted on it’s axis by 23.5 on it’s axis by 23.5º º During certain times of the year, we During certain times of the year, we

receive more direct sunlight since we are receive more direct sunlight since we are tilted toward the Sun (Summer)tilted toward the Sun (Summer)

Other times we receive less direct sunlight Other times we receive less direct sunlight since we are tilted away from the Sun since we are tilted away from the Sun (Winter)(Winter)

SeasonsSeasons

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Equinoxes and SolsticesEquinoxes and Solstices

Autumnal and Vernal Equinox occur in Autumnal and Vernal Equinox occur in September and March respectivelySeptember and March respectively

Equinox “Equal Night”Equinox “Equal Night”Summer Solstice Longest DaySummer Solstice Longest DayWinter Solstice Shortest Day Winter Solstice Shortest Day These rules are for Northern HemisphereThese rules are for Northern Hemisphere! !

Seasonal SunSeasonal Sun

Does the sun appear at the same location Does the sun appear at the same location in the sky at “noon” from season to in the sky at “noon” from season to season?season?

No! How does it change?No! How does it change?Pg. 8 of Text demonstrates thisPg. 8 of Text demonstrates thisTilt of Earth affects the location of SunTilt of Earth affects the location of Sun

Seasonal SunsetSeasonal Sunset

The tilt also affects the location of the The tilt also affects the location of the sunrise and sunsetsunrise and sunset

Pg. 9 of TextPg. 9 of TextSun’s position moves Southward Sun’s position moves Southward

approaching the Winter Solsticeapproaching the Winter Solstice It moves Northward approaching the It moves Northward approaching the

Summer SolsticeSummer SolsticeThink about the motion during the course Think about the motion during the course

of the yearof the year

Larger MotionsLarger Motions

Notice the night sky during different times Notice the night sky during different times of the yearof the year

Different star groupings are visible at night Different star groupings are visible at night during different times of the yearduring different times of the year

Why? We are orbiting the Sun!Why? We are orbiting the Sun!Year-time for one complete orbit around Year-time for one complete orbit around

the Sun by the Earththe Sun by the Earth

Other Larger MotionsOther Larger Motions

During the course of the year both the Sun During the course of the year both the Sun and Moon appear to be moving and Moon appear to be moving EastwardEastward compared to the background starscompared to the background stars

Sun –due to Earth’s orbitSun –due to Earth’s orbitMoon –due to it’s orbit`Moon –due to it’s orbit`

What’s Your Sign?What’s Your Sign?

Constellations- Apparent 2-D picturesConstellations- Apparent 2-D picturesZodiac-12 constellations that are special Zodiac-12 constellations that are special Lie along Lie along EclipticEcliptic, the apparent path of the , the apparent path of the

Sun through the sky due to the tilt of the Sun through the sky due to the tilt of the EarthEarth

Sun in LeoSun in Leo

When we identify the Zodiac constellations When we identify the Zodiac constellations we reference the position of the Sunwe reference the position of the Sun

Can we actually see Leo from the earth Can we actually see Leo from the earth during the month of August?during the month of August?

No, the Sun is much too bright!No, the Sun is much too bright!We need to wait until later Winter to see We need to wait until later Winter to see

Leo in the nighttime skyLeo in the nighttime sky

Phases of the MoonPhases of the Moon

Why do we see the phases of the MoonWhy do we see the phases of the Moon??

AnswerAnswer

The relative positions of the Earth, Moon, The relative positions of the Earth, Moon, and Sunand Sun

Waxing- Moon is getting brighter (New to Waxing- Moon is getting brighter (New to Full)Full)

Waning-Moon is getting darker (Full to Waning-Moon is getting darker (Full to New)New)

Month-one complete phase cycle of the Month-one complete phase cycle of the moonmoon

earth

moon orbit`searth

last (third)quarter

gibbous moon

full moon

gibbous moon

first quarter

crescent

new moon

crescent

waning Moon

waxing Moon

SUN

Moon Bow and ArrowMoon Bow and Arrow

The lighted portion of the Moon always The lighted portion of the Moon always points toward the Sunpoints toward the Sun

The angle between the Sun and Moon The angle between the Sun and Moon changes as the Moon goes through its changes as the Moon goes through its phase cyclephase cycle

Arm exercise on pg 13 of textArm exercise on pg 13 of text

EclipsesEclipses

Are caused by shadows cast on objectsAre caused by shadows cast on objectsSolar EclipseSolar Eclipse-Moon blocks light from the -Moon blocks light from the

Sun and casts a shadow on the EarthSun and casts a shadow on the EarthLunar EclipseLunar Eclipse-Earth blocks light from the -Earth blocks light from the

Sun and casts a shadow on the MoonSun and casts a shadow on the Moon

Solar EclipseSolar Eclipse

Moon must be between the Sun and EarthMoon must be between the Sun and EarthMoon must be in what phase for a Solar Moon must be in what phase for a Solar

Eclipse to occur?Eclipse to occur?NewNew

Eclipses don’t occur every month due to Eclipses don’t occur every month due to tilts of both Earth’s and Moon’s orbittilts of both Earth’s and Moon’s orbit

Solar Eclipse PanoramaSolar Eclipse Panorama

Astronomy Picture of the Day

Lunar EclipseLunar Eclipse

Earth must be between Sun and MoonEarth must be between Sun and MoonMoon must be in what phase ?Moon must be in what phase ?

FullFullMore people can see it since Earth’s More people can see it since Earth’s

shadow is largershadow is larger

Lunar Eclipse MontageLunar Eclipse Montage

Planetary MotionsPlanetary Motions

Planet –”wanderer”Planet –”wanderer”Do appear to rise in East and set in WestDo appear to rise in East and set in West

BUT….BUT….Don’t follow a consistent motion through Don’t follow a consistent motion through

the sky compared to the back ground starsthe sky compared to the back ground starsMost times the planets do move Eastward Most times the planets do move Eastward

like Sun and Moon (prograde)like Sun and Moon (prograde)

Planetary Motions IIPlanetary Motions II

But…occasionally these planets appear to But…occasionally these planets appear to move move WESTWARD WESTWARD compared to the starscompared to the stars

Retrograde Motion –backward motionRetrograde Motion –backward motionWhy does this happen?Why does this happen?We’ll see that soon!We’ll see that soon!

Human AnatomyHuman Anatomy

You have all the tools that ancient You have all the tools that ancient astronomers had!astronomers had!

EyesEyesHandsHandsBrainsBrainsPg. 6 of Text will show you how to put Pg. 6 of Text will show you how to put

these to usethese to use

SummarySummary

You know much already about You know much already about observational Astronomyobservational Astronomy

Anyone can be an AstronomerAnyone can be an AstronomerHeavenly objects follow predictable Heavenly objects follow predictable

motions. Some units of time are defined by motions. Some units of time are defined by these motionsthese motions

Appearance of objects can change for a Appearance of objects can change for a variety of reasonsvariety of reasons