] Starry Night Times
Simulation Curriculum

For education orders please call 1-877-290-8256.

Welcome to the July Third Week Featured Article!

Sunset on the Moon

Geoff Gaherty, Starry Night Education

The most common sight in the night sky is the waxing Moon, which we have been watching over the past two weeks.

Usually we are seeing the Sun rising over the mountains and craters of the Moon. This week is an opportunity to watch the Sun set. But, where is the Moon? Credit: Starry Night software.
Usually we are seeing the Sun rising over the mountains and craters of the Moon. This week is an opportunity to watch the Sun set. But, where is the Moon? Credit: Starry Night software.

Starting just after New Moon as a slender crescent, the Moon grew to first quarter on July 5, and was full on July 12. If you were paying attention, you would have noticed that the Moon rose and set about 50 minutes each night, moving against the background stars in its monthly orbit around the Earth. Last weekend the Full Moon rose just at sunset.

But where is the Moon now? If you look at the evening sky, it’s nowhere to be seen. The answer lies in the fact that it rises 50 minutes later each night. Tonight, July 16, it won’t rise until about 11:30 p.m., and won’t be high enough to observe with a telescope until about 1 a.m. So you will need to stay up late to observe the Moon this week.

There is an alternative: if you get up early in the morning and look towards the south, you will see the Moon riding high in the daytime sky. The Moon is crossing the meridian just at sunrise tomorrow morning, around 6 a.m.

To the casual observer, the Moon’s behavior may seem capricious, but it all follows simple laws. The Earth rotates once every 24 hours, which makes nearly everything in the sky, including the Moon, rise every 24 hours in the east, and set every 24 hours in the west. The only exceptions are the stars close to the celestial poles, which are above the horizon all the time.

The second basic motion of the Moon is its revolution in orbit around Earth once every 27.4 days. This motion is only noticeable when the Moon passes close to a bright planet or star, as it did last week with Mars and Saturn.

The third factor is the path the Moon follows through the stars, called the ecliptic. This is tilted by 23 degrees to the celestial equator, so that the Moon appears to shift north and south.

There have been a number of videos on YouTube recently claiming that the Moon is "off its axis." All of these apparitions of the Moon are easily explained by the three motions described above. In fact, the Moon has been following these patterns like clockwork for millions of years, and nothing has changed.

If you have a telescope, try to take a look at the Moon this week. Its topography will look rather different from what you are used to. Most of the time we observe the Moon around first quarter, when the Sun is rising in the east (to our right) over the surface of the Moon.

This week, the Sun is setting towards the Moon’s western horizon, to our left, and we see the landscape lit from the left, the opposite direction to what we’re used to.

Perhaps the most striking difference is the Straight Wall or Rupes Recta, a scarp located close to the eastern edge of the Mare Nubium, just south of the center of the Moon’s disk. Just after first quarter, this appears as a long dark line, a shadow cast by the rising Sun.

Just before last quarter, the Straight Wall is instead lit from the left, so that its face appears, fully lit by the setting Sun, as a bright white line.

Something else you may notice in a telescope looking at the lunar surface this week is an interesting optical illusion. Because the light is coming from an unexpected direction, the lunar surface at high magnifications sometimes appears to invert, so that craters appear as mountains and vice versa. Stare a little longer, and it will usually revert to its normal appearance.

Many years ago, I made systematic pencil sketches of a number of lunar landmarks. I always tried to make at least one drawing with the lighting coming from the opposite direction. This often revealed subtle features in the lunar topography.

I encourage every amateur astronomer to attempt pencil sketches of the things they observe through their telescope. It’s amazing how much more your eye can see when you try to sketch. Don’t think of it as "art," but rather as an attempt to record as accurately as possible the pattern of light and dark that you see.

Coming Events

Here is a rundown of events coming soon to a sky near you!

Moon Phases

Saturday, July 5, 7:59 a.m. EDT

First Quarter Moon

The First Quarter Moon rises around 1:45 p.m. and sets around 1:15 a.m. It dominates the evening sky. First Quarter Moon Credit: Starry Night software.

Saturday, July 12, 7:25 a.m. EDT

Full Moon

The Full Moon of July is known as the Hay Moon, Buck Moon or Thunder Moon. It rises around sunset and sets around sunrise, the only night in the month when the Moon is in the sky all night long. The rest of the month, the Moon spends at least some time in the daytime sky. July Full Moon Credit: Starry Night software.

Friday, July 18, 10:08 p.m. EDT

Last Quarter Moon

The Last Quarter Moon rises around 12:30 a.m. and sets around 2:30 p.m. It is most easily seen just after sunrise in the southern sky. July Last Quarter Moon Credit: Starry Night software.

Saturday, July 26, 6:42 p.m. EDT

New Moon

The Moon is not visible on the date of New Moon because it is too close to the Sun, but can be seen low in the East as a narrow crescent a morning or two before, just before sunrise. It is visible low in the West an evening or two after New Moon. July New Moon Credit: Starry Night software.

Observing Highlights

Friday, July 4, 4 a.m. EDT

Pluto at opposition

Dwarf planet Pluto reaches opposition with the Sun in eastern Sagittarius. It is moving away from the richest part of the Milky Way, so is not quite as lost amongst rich star fields as it has been in recent years. Pluto at opposition Credit: Starry Night software.

Saturday, July 5, 9 p.m. EDT

Mars and the Moon

The waxing gibbous Moon will pass just north of the planet Mars. Observers in Hawaii, western Central America, and northern South America will see the Moon occult Mars. Mars and Moon Credit: Starry Night software.

Monday, July 7, 10 p.m. EDT

Saturn and the Moon

The Moon will pass just south of the planet Saturn. The Moon will occult Saturn as seen from French Polynesia, southern South America, and South Georgia and South Sandwich Islands. Saturn and the Moon Credit: Starry Night software.

Saturday, July 12, dawn

Mercury at greatest elongation

Not a particularly good apparition of Mercury, though slightly better as seen from the Southern Hemisphere here. Look half an hour before sunrise with binoculars, using Venus and nearby bright stars to locate Mercury. Mercury at greatest elongation Credit: Starry Night software.

Saturday, July 12, dusk

Mars and Spica

Mars passes less than 2 degrees north of the bright star Spica, Alpha Virginis. Look for the pair about an hour after sunset. Mars and Spica Credit: Starry Night software.

Tuesday, July 22, dawn

Aldebaran and the Moon

The Moon passes just north of the bright star Aldebaran in Taurus. Look for Venus and Mercury below and to their left, and follow the shrinking crescent Moon over the next few nights as it slides below Venus and Mercury. Aldebaran and the Moon Credit: Starry Night software.


Planets

Mercury will be low in the dawn sky all month. This is not a very good apparition of Mercury, though being close to Venus will help you to find it. This is the view half an hour before sunrise in the Northern Hemisphere. Mercury: Starry Night software.

Venus is low in the eastern sky, rising just before the Sun. Venus: Starry Night software.

Mars is now fading rapidly in brightness as it moves towards the far side of the Sun.
Mars: Starry Night software.

Jupiter is too close to the Sun to be observed, being in conjunction on July 24.

Saturn, in Libra, is well placed in the evening sky. Saturn: Starry Night software.

Uranus is located in the constellation Pisces, rising near midnight. Uranus: Starry Night software.

Neptune is in Aquarius all month, rising in the late evening. Neptune: Starry Night software.


gifspacer gifspacer gifspacer
Feedback
gifspacer

   
Send us your feedback

Do you have a question, comment, suggestion or article idea to pass along to Starry Night® Times?

Click here to get in touch with us.
   

gifspacer
Feedback
Follow Us on Twitter
Educational Inquiries and Sales

   
Follow us at
• twitter.com/starrynightedu
   

Educational Inquiries and Sales
Educational Inquiries and Sales
gifspacer gifspacer gifspacer
Educational Inquiries and Sales
Educational Inquiries and Sales

   
Educational Inquiries and Sales

Please contact us for all education inquiries. EDUCATION ORDERS 1-877-290-8256
   

Educational Inquiries and Sales
Educational Inquiries and Sales
gifspacer gifspacer gifspacer
Subscriptions
gifspacer

   
Starry Night®
is the world's leading line of educational astronomy software and DVDs. Visit store.simulationcurriculum.com to see all the great products we offer for everyone from novice to experienced astronomers.

You have received this e-mail as a user of Starry Night® or as a registrant at starrynighteducation.com.

Starry Night® is a division of Simulation Curriculum Corp.

Simulation Curriculum Corp.
Starry Night® Education

11900 Wayzata Blvd.
Suite 126
Minnetonka, MN 55305
Tel: 1-866-688-4175
   

gifspacer
Subs

© 2016 Simulation Curriculum Corp. All Rights Reserved.