Here’s a morning exercise for this week! I thought of this one to demonstrate to our daughters “how the Moon grows old and becomes new again”.
You can try this late at night if you’re a nightowl or mornings as you’re on the way out to start your day.
The Moon reached last quarter on July 4th and will be ”new” on July 11th
You’ll need a clear view to the east and west. Once outside, look for the Moon above the western horizon (where the Sun sets). The earlier in the week you do this for the first time the better.
Once you’ve found the Moon make a mental note of its position relative to the Sun and its “phase” which is the amount of the Moon’s disc that’s lit by sunlight. The Moon’s western limb (the left side in your view) will be in sunlight and its eastern limb (to your right) in an ever widening shadow. Each day the Moon will rise and set about 25 minutes later and appear about 15 degrees further east, nearer the Sun, and a smaller part of its disc will be sunlit. Make mental note of the Moon’s changing position relative to the Sun and phase from day to day. Try to make your observations at or about the same time each morning.
The line separating the lit and dark areas of the Moon is called the “terminator”. As the Moon wanes the terminator is where the Sun is setting. The terminator is the place to point your telescope or binoculars as the Moon waxes or wanes because this is the area where surface features like craters and mountain peaks stand out in shadowed relief. Consider how the shadows are longest at sunrise and sunset here on Earth and you’ll get the idea.
After watching this celestial dance for two or three days I hope you will have a sense of how the Moon’s orbit brings her apparent position closer to the Sun and the start of a “new” lunation or lunar cycle. On the mornings of the 8th through 10th the Moon will be just west of (rising before) the Sun at dawn. “New” Moon on the 11th will find our Moon with her back to the Sun. In other words, the far side of the Moon will be “full” as the side facing Earth is “new”. From the 12th on she’ll be east of (setting after) sunset. My favorite days for moon watching are very thin crescent waning (old) or waxing (new) phases. So go out and watch her naked eye or better yet with your binoculars or telescope mornings just before or evenings just after “new” July 8th through 12th.
There will be a total solar eclipse coincident with the new Moon on July 11th but it will be visible only in the South Pacific. This eclipse compliments the partial Lunar eclipse which took place June 26th at the last Full Moon. As the Moon begins the next Lunation she will pass just 7 degrees below and left of Venus on the 14th and approximately the same distance from Mars on the 15th.
I took the above image one morning at about 4am in September, 2004. It shows the waning crescent Moon and one of my favorite craters, Gassendi. Click on the image to enlarge it and look closely and you can see shadows cast by the peaks on the eastern rim of the crater. When this image was taken it was late afternoon in that area of the Moon.
Here’s a quiz for you:
How long is a “day” on the Moon? Meaning sunrise to sunset.
a)one day, b)28 days, c)one month, d)28 hours.
To assist your moonwatching activities here is a list of Moonrise/set times based on Louisville, KY for the week of July 4-11. Times are listed in 24 hour “military” format. Example: July 5 moonrise was 1:16am, moonset 3:11pm EDT
July 05 0116 1511
July 06 0146 1614
July 07 0222 1719
July 08 0305 1823
July 09 0357 1925
July 10 0459 2021
July 11 0610 2109