Introduction to AstronomyName: Nicole Shetka

Sci 135-B1Spring 2009

Worksheet 5.2 – Moon Phases and Eclipses

When you answer the following questions, please show your reasoning, explaining in full sentences how you got your answer. If you wish to include a picture that you did not create yourself, you MUST include the source for where you got it. Assume you are in the Northern Hemisphere of the Earth. Feel free to refer to the diagrams and tables from lecture, the diagrams from Worksheet 5.1, or to the Sky Charts 2 and 3 from last week.

  1. Going from New Moon to Full Moon, is the right or left side lit up as seen from the Earth?

This is a difficult question since most maps have the sun on both sides. But the answer is the near side of the moon is constantly lit up by the sun. The moon rotates the earth. The same side of the moon is constantly seen. There is no “sides” that can be defined since when it rises you see one side and when it sets the “side” of the moon has flipped. So it rises in the east and you see the “left” lit up and sets in the west with the “right” lit up. You also see it this way as right or left lit up if you look at the moon straight up in the sky and face frontwards or backwards.

Side note: the moon on Feb. 22nd had a massive halo around it from the impending weather. It was pretty.

  1. Why isn’t there a lunar or solar eclipse every month?

Because in order for there to be an eclipse the moon must be in one of 2 places.

The “nodes” as shown the picture above from Hermit.org shows where these

places are. As the whole earth/moon orbits the sun twice a year, the nodes will

line up to give us an eclipse. This is why eclipses do not happen every month.

  1. If you were standing on the Earth as it passed through the Moon’s umbra, what would you see?

You would see a full solar eclipse.

  1. What causes an annular eclipse?

In what part of the Moon’s shadow is your part of the Earth? An annular eclipse is caused when the moon covers the center of the sun but is far away so the umbra of the moon does not touch the earth. The penumbra does reach the earth though so those in other parts can see a partial eclipse.

  1. If there were a solar eclipse on the date of the Autumnal Equinox, what would be the Moon’s RA and Dec?

The RA and Dec are RA: 21hr 22mn Dec. -16 degrees

  1. What if it were a lunar eclipse on the Autumnal Equinox?

RA 10hr 14min Dec. +10 degrees

  1. What about a lunar eclipse on the Winter Solstice?

RA 5hr 57 min Dec. +23 degrees

  1. And what is the Moon’s Alt/Az at transit when there is a lunar eclipse on the Winter Solstice?

Altitude 43 degrees, Azmith 74 degrees. This is a guess from this map of the upcoming Lunar Eclipse on Dec. 21, 2010 from NASA

arrow pointing to Massachusetts. We seem to be in a good position to

see the upcoming eclipse.

All RA/Dec information was attained from the Nasa website on Eclipses. The other answers where found while reading the hermit.org on lunar and solar eclipses and the powerpoint slides from class.