ASTR 1514 1st Edition Lecture 2Motions of the sky in one year brief overview- Average distance from Earth to sun – AU or Astronomical Unit = 150 million Km- Earth’s rotational axis tilt is 23.5 degrees, cause of the seasons.- The Suns motion on the ecliptic reflects the Earths motion around the sunMotions of the Moon- Orbit of the Moon Approximately 27.322 days. The moon has different phases in which a different portion shines at differenttimes throughout its orbit. The orbit of the moon determines the visibility of the moon to an observer on Earth. The moon shines by reflecting light from the sun, the moon is only ever halfway lit, but we cannot always see the entire lit half. The moon orbits in the same direction as the Earth orbits around the sun, and the same direction the Earth revolves. The moon has a Synchronous rotation, meaning it completes one full rotationin one full orbit around the Earth. Phases of the Moon- Phases of the moon are determined by how much of the bright side that we see.There are 8 different phases of the moon throughout its 27-28 day orbit around the Earth.- Waning – To decrease in size- Waxing – To increase in size1.New Moon – Completely Dark2.Waxing Crescent – Illuminating crescent appears to increase in size3.First Quarter – Moon appears to be half a circle in sky (occurs about 7 days into moons orbit)4.Waxing Gibbous – Small portion of moon is dark, appears to increase in size.5.Full Moon – Moon appears to be a complete circle (occurs about 14th day of moons orbit.)6.Waning Gibbous –Small portion of moon is dark, appears to decrease in size. 7.Third Quarter – Moon appears to be half circle in sky (occurs about the 21st day of moons orbit around Earth.)8.Waning Gibbous – Illuminated crescent appears to decrease in size.Here is a Diagram of the Phases of the Moon-The Earth rotates counter clock-wise, therefore the moon rotates counter-clockwise. Helpful Questions1.) What time is the full moon directly overhead? Midnight is when the full moon phase isat it’s highest point from earths perspective.2.) What time does the first quarter moon set? Midnight. It helps to find out when each moon sets and
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