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Solar Eclipse 2017

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The Night Sky Tonight: September 23 – October 1

By Mark Wagner

Friday, September 23
This morning's last quarter Moon offers an outstanding view of two rilles, visible best with 200mm instruments or larger. Lunar Moon Atlas describes Hyginus Rille as: "Large rille South-East North-West oriented to the departure. Crosses the crater Hyginus. Then West East oriented. Few Deep. Seems formed of an alignment of craterlets. Connected by a small groove to Rima Ariadaeus." Triesnecker Rille is described as: "Very ramified rilles system spreading the North slope of Rhaeticus to Rima Hyginus and situated on the slope East slope of Triesnecker. The densest of the visible face of the Moon. Comprises 5 North South oriented main rilles."

Skill Level: Beginner

Suggested Gear: Orion SkyQuest XT8 Classic Dobsonian Telescope, Orion MoonMap 260

Tomorrow evening: M15 globular cluster in Pegasus

Saturday, September 24
After looking at the double star Enif earlier this week, it?s easy to jump up to M15, a terrific globular cluster in line with the two end stars of the neck of Pegasus. M15 was discovered by Jean-Dominique Maraldi in 1746, and included in the Messier Catalog. It is highly condensed at its core and in a 10 inch or larger instrument breaks up into hundreds of resolved stars. It is one of the larger such clusters at 18 arc-minutes in diameter, 33,600 light years away, and, at an estimated 12 billion years of age, it is one of the oldest objects we know of.

Skill Level: Intermediate

Suggested Gear: Orion SkyQuest XT10 Classic Dobsonian Telescope, Orion DeepMap 600 Folding Star Chart

Tomorrow morning: Terms Right Ascension and Declination

Sunday, September 25
The sky is divided into a grid to help us know where to locate objects of interest to us. Declination is based on the celestial equator, which is 0 degrees declination. To the north declination is a positive number, below the celestial equator numbers are negative. Lines of "right ascension" run between our north and south poles, dividing the sky up by hours. Here we see hours 4 and 6 of the 24 hours of demarcation in our sky. Learn to navigate by "R.A." and declination, and you can find anything in the sky.

Skill Level: Beginner

Suggested Gear: Orion Star Target Planisphere, 30-50 degree, Orion DeepMap 600 Folding Star Chart

Tomorrow evening: Planet on display

Monday, September 26
Mars, Saturn and Venus are on display arcing down across the southwestern horizon 40 minutes after sunset. By the time the sky is fully dark, Venus will have dropped below the horizon. Their magnitudes are 0.02, 0.53 and -3.93 respectively. Can you also pick out Antares, the heart of Scorpius below Saturn at magnitude 1.03? This configuration of Mars, Saturn and Venus will persist for weeks, with Venus incrementally gaining a bit of altitude.

Skill Level: Beginner

Suggested Gear: Orion AstroView 90mm Equatorial Refractor Telescope, Orion DeepMap 600 Folding Star Chart

Tomorrow morning: The constellation Leo, with Regulus and the Moon

Tuesday, September 27
Leo is fully risen over the eastern horizon by astronomical dark. Its alpha star (A), its brightest, is Regulus, 78 light years distant shining at magnitude 1.34. At 11 hours 58 minutes declination, Regulus is in the wandering path of the Moon, and tonight a waning crescent Moon illuminated just 11% is about 4.5 degrees to its west. If you have a low eastern horizon you'll also be able to pick out Mercury. Leo is an ancient constellation, one of the original 48 described by Ptolemy in the 2nd century.

Skill Level: Beginner

Suggested Gear: Orion Scenix 10x50 Wide-Angle Binoculars, Orion DeepMap 600 Folding Star Chart

Tomorrow evening: Aquila soars in the south!

Wednesday, September 28
Aquila is a summer constellation straddling the dark rift of our Milky Way Galaxy. It is often referred to as the graveyard of stars, as it contains many planetary nebulae. Altair is the alpha star (A), bright white at magnitude 0.75 and only 17 light years from us. Along with Deneb in Cygnus and Vega in Lyra, Altair is part of the famous Summer Triangle asterism. 2nd century A.D. astronomer Ptolemy included Aquila in his original 48 constellations, but it is mentioned as far back as Exodus, in the 4th century B.C.

Skill Level: Beginner

Suggested Gear: Orion DeepMap 600 Folding Star Chart, Orion Star Target Planisphere, 30-50 degree

Tomorrow morning: A bright non-Messier galaxy in Leo

Thursday, September 29
It?s hard to believe Charles Messier missed this bright galaxy during his nights of comet hunting. Bright at magnitude 9.57 and large at 12.6 x 6.0 arc-minutes, NGC 2903 can be viewed even from suburban skies. It is an easy star-hop off the stars that form the sickle, or backward question mark of Leo. With larger telescopes, the star forming region NGC 2905 can be viewed in one of the spiral extensions. One observation report has this galaxy observed in 9x63 binoculars from magnitude 5.2 skies in Canada!

Skill Level: Beginner

Suggested Gear: Orion SkyQuest XT10i IntelliScope Dobsonian Telescope, Orion DeepMap 600 Folding Star Chart

Tomorrow: Second New Moon this month!

Friday, September 30
Today is the second New Moon in the same month; a deep sky observer's dream! When we have two Full Moons in a month, the second one is called a Blue Moon. What should we call the second New Moon in the same month? Suggestions? Here you can see why we can't observe the Moon when its new. Today's New Moon is just west of the Sun. When the Moon happens to pass in front of the Sun, we get a solar eclipse. Have you ever seen one? Did you know the United States will get a total solar eclipse next August?

Skill Level: Beginner

Suggested Gear: Orion Telescope Observer's Guide, Orion Star Target Planisphere, 30-50 degree

Tomorrow evening: A few deep sky challenges in Aquila

Saturday, October 1
Here are two very different types of deep sky objects that will test your skills. NGC 6751, shown in a drawing here, is a planetary nebula (a dying star). Its position is easy, off two stars in the tail of Aquila the Eagle. At 6,500 light years away, it appear as a small smoke ring in a telescope. It is dim at magnitude 12.5, and 20 arc-seconds in diameter. NGC 6760 is a challenging globular cluster, near a pair of 5th magnitude stars. Its 8.88 magnitude is deceiving, it will appear dimmer, with a size of 13 arc-minutes, 24,000 light years from home. Anyone here up to this challenge?

Skill Level: Advanced

Suggested Gear: Orion SkyQuest XT12i IntelliScope Dobsonian Telescope, 2" Orion UltraBlock Narrowband Eyepiece Filter

Tomorrow morning: An easy asterism in Leo

Charts from Starry Night Pro, available from Orion Telescopes & Binoculars. Lunar images from Virtual Moon Atlas. M15, NGC 2903 and NGC 6760 images from Wikisky.org. Penumbral image courtesy NASA. NGC 6751 drawing from Dr. Johannes Schilling. All data from Starry Night Pro 6 and Wikipedia.

Mark Wagner is a life-long astronomy enthusiast and deep sky observer in the San Francisco bay area. Visit our Facebook Page if you'd like to post comments, questions, sketches or images you've taken on the our Night Sky Tonight sky charts.