Astro 120 Fall 2005: Lecture 5 page 1
•The Sun on the Meridian Diagram
•altitude at noon at equinox
•altitude at noon at summer/winter solstice
•The Ecliptic
•sun moves eastward along the ecliptic
•inclination of the ecliptic = 23.5 degrees to celestial equator
•crossing points are equinoxes; extrema are solstices
•The Seasons
•azimuth of sunrise/sunset at various latitudes
•length of time above the horizon in summer and winter
•angle of sunlight shallower in winter than in summer
•distance is NOT a factor
•The Motion of the Moon
•eastward motion in orbit around the Earth
Brief review of last time: Time and The Seasons
Reading: Bennett, Chapter 2, Sections 2.5
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Problem Set #1:
Available NOW on the Astro 120 Website; Due 9/9-12
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Astro 120 Fall 2005: Lecture 5 page 2
The Motion(s) of the Moon
•eastward motion with respect to the stars
•orbit
of
the
Moon
around
the
Earth
caused by
Complete circle in one sidereal month = 27.3 days
Rate of motion is about 13 degrees/day
Time between successive full moons is 29.5 days
This is the synodic month
BUT
start
Astro 120 Fall 2005: Lecture 5 page 3Astro 120 Fall 2005: Lecture 5 page 4
The Phases of the Moon
6PM
6AM
noonmidntnew
Full
1st Quarter
3rd Quarter
CRESCENT
GIBBOUS
GIBBOUS
CRESCENT
Waning
Waxing
