7/31/2019 Lunar Slides

1/6

New 0% Illuminated Waxing Crescent 25% Illuminated on RHS

First Quarter 50% Illuminated on RHS

Waxing Gibbous 75% Illuminated on RHS Full 100% Illuminated

Waning Gibbous 75% Illuminated on LHS

Third (Last) Quarter 50% Illuminated on LHS Waning Crescent 25% Illuminated on LHS

Phases of the Moon

7/31/2019 Lunar Slides

2/6

Rising/Meridian/Setting Times

Phase Rising Meridian SettingNew 6 am Noon 6 pm

Waxing Crescent 9 am 3 pm 9 pm

First Quarter Noon 6 pm MidnightWaxing Crescent 3 pm 9 pm 3 am

Full 6 pm Midnight 6 am

Waning Gibbous 9 pm 3 am 9 amThird Quarter Midnight 6 am Noon

Waning Crescent 3 am 9 am 3 pm

*Assuming the moon is always on the celestial equator and above thehorizon 12 hours per day.

7/31/2019 Lunar Slides

3/6

Lunar Periods

Sidereal Period 27.3 days

The time between successive alignmentsof the earth, moon, and a star

The true orbital period of the moon

Synodic Period 29.5 days

The time between successive alignmentsof the earth, moon, and the sun

The period of the cycle of lunar phases

7/31/2019 Lunar Slides

4/6

Lunar Eclipses

Total Lunar Eclipse The moon is entirely inside the earths umbra

Partial Lunar Eclipse

The moon is partially inside the earthsumbra

Penumbral Lunar Eclipse

The moon is inside the Earths penumbra

These happen regularly and no one notices.The brightness of the moon only decreasesby 10% to 20%

7/31/2019 Lunar Slides

5/6

Solar Eclipses Total Solar Eclipse

The moon completely obscures the sun for anobserver at this location on the Earth

Partial Solar Eclipse

The moon partially obscures the sun for anobserver at this location on the Earth

Annular Solar Eclipse The moon is near apogee and its angular

diameter is insufficient to completely coverthe sun. An observer for whom the moon andsun are aligned will see a ring of the sunaround the moon

7/31/2019 Lunar Slides

6/6

Tides- caused by differential gravitational forces exerted

by the moon (the moon pulls more on one side ofthe earth than the other)- Even though the suns gravitational force is much

larger than the moons, its differential force issmaller (since the size of the earth is small

compared to the earth-sun distance)- This moons differential force causes water bulges

on the earth on both sides of the line to the moon.Tides are caused by the Earths rotation carrying

observers through a water bulge. Thus, typicallyhigh tide occurs twice a day.- Neap Tidesweak tides which occur when the moons

and suns pull are perpendicular- Spring Tides strong tides when the moon and sun are

aligned.