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The Night Sky Tonight: December 2 – December 10

By Mark Wagner

Friday, December 2
The constellation Canes Venatici shares an asterism with three others. Its alpha star Cor Caroli forms one point of the Diamond Of Virgo. Arcturus is the alpha star of Bootes, Spica is Virgo's alpha, and Denebola in Leo is its beta (second brightest) star. Jupiter is certainly prominent on the border of the Diamond of Virgo tonight! This part of the night sky, within the diamond, is rich in deep sky targets, containing an area called the Realm of the Galaxies.

Skill Level: Beginner

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

Tomorrow evening: Double star challenge

Saturday, December 3
65 Piscium (Struve 61) is a fine matched pair double star high in the constellation Pisces, near Delta Andromedae (D). Use Beta Andromedae to find Delta, then drop down at a right angle about half that distance to find Delta. 65 Piscium is a pair of magnitude 6.3 white stars separated by about 4.5 arc-seconds. They will just begin splitting apart at 100X, and be easier to separate at 165x. I am unable to find a distance to this pair — can anyone help? While you're out, don't miss the nice view of the Moon and Venus 6.3 degrees apart, along with Mars, in the southern sky.

Skill Level: Intermediate

Suggested Gear: Orion DeepMap 600 Folding Star Chart, Orion SpaceProbe 130 EQ Reflector Telescope

Tomorrow morning: Constellation Coma Berenices

Sunday, December 4
The constellation Coma Berenices is ancient, dating to the 3rd century B.C. and included in Ptolemy's original 48 constellations in the 2nd century A.D. Its beta (B) star is actually brighter at magnitude 4.26 than the alpha (A). Along with Gamma Comae Berenices, the three stars form an isosceles triangle. Our galactic north pole is located between beta and gamma, next to the magnitude 4.9 star 31 Comae Berenices. As such we look perpendicular and away from the dusty plane of our own galaxy, into unobstructed deep space and rich fields of very distant galaxies. Coma Berenices is rich, containing two open clusters, several globular clusters and eight Messier objects! Who can describe the story behind the name Coma Berenices?

Skill Level: Beginner

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

Tomorrow evening: Planets, Moon, Mars and Venus

Monday, December 5
Tonight is a solar system treat, with four bright objects lined up spanning three constellations. Get out about 35 minutes after sunset to try catching Mercury before it sets, almost exactly to the southwest. Mercury is magnitude -0.49 1.12 A.U. from Earth and 24 degrees from Venus. Venus shines brilliantly at magnitude -4.17 (the third brightest object in our skies) less than 1 A.U. from Earth, and almost 22 degrees from magnitude 0.67 Mars, which is 1.47 A.U. from us and growing more distant. The Moon is just over 8 degrees past Mars, a rather average 386,000 kilometers away in its orbit around Earth, at a waxing crescent 36% illumination at magnitude -11.68. It is easy to visualize the path of the ecliptic, and the Zodiac looking at these objects tonight!

Skill Level: Beginner

Suggested Gear: Orion AstroView 90mm Equatorial Refractor Telescope, Orion Star Target Planisphere, 30-50 degree

Tomorrow morning: Binocular astronomy in Coma Berenices

Tuesday, December 6
If you're in a darkish location, you'll be able to view Melotte 111 as a triangular patch of stars high in Coma Berenices this morning. This is a nearby open cluster aptly named the Coma Star Cluster, only 288 light years away (closer than many stars we see in the night sky). It contains about 50 stars from near magnitude 5 to magnitude 10, covering an area of more than 5 degrees. Its large size is a function of its close proximity to us. Use your binoculars to scan the area from suburban skies, in order to see the members of this cluster.


Tomorrow evening: Observe the first quarter Moon

Wednesday, December 7
Tonight's first quarter Moon offers a few really great observing targets. Plato is next to the terminator and will be high contrast. Plato is a 101 km wide crater with a bright rim and flat dark floor. It should feature a 2.2 km high central peak, but it is buried under a fill of lava 2.6 kilometers deep. Plato disrupts the Lunar Alps. Moretus is near the lunar south pole, and will be a dramatic sight tonight. It features an imposing central peak 2,700 km in height, a flat floor filled with dark lava, hills, craterlets, and very high walls with terraces. Someone should sketch this and send it in to me!

Skill Level: Beginner

Suggested Gear: Orion Observer 70mm Altazimuth Refractor Telescope, Orion MoonMap 260

Tomorrow morning: NGC 4565 in Coma Berenices

Thursday, December 8
NGC 4565 is one of the truly great galaxies visible in a telescope. Sitting near the edge of the Coma star cluster, this edge on galaxy has been viewed in 6 inch telescopes. Look for a needle-like extension of the spiral arms viewed on their edge, a central bulge with a bright star almost superimposed, and with darker skies and magnification a dark lane nearly bisecting the spiral arms. If you can't see it from your observing site, put it on your list for a dark sky evening. NGC 4565 is one of the non-Messier galaxies that is always a treat to observe!

Skill Level: Intermediate

Suggested Gear: Orion SkyQuest XT10 Classic Dobsonian Telescope, Orion SkyQuest XX12i IntelliScope Truss Dobsonian Telescope

Tomorrow evening: Bright double star Gamma Arieti

Friday, December 9
With a big Moon out tonight, double stars are about all we can see aside from the Moon itself. But, if you can see the Alpha (A) and Beta (B) stars in Aries, just east of the Moon, you should be able to ferret out Gamma Arietis (Mesarthim), a fine binary star. Distance estimates vary from 164 to 204 light years. Its combined magnitude is 3.87, with two nearly equally bright components (4.58 and 4.64 magnitudes) separated by 7.6 arc-seconds, resolvable in a small telescope. This double was first noted in 1664 by the astronomer Robert Hooke. In Sanskrit its called Mesha, the Ram.

Skill Level: Intermediate

Suggested Gear: Orion AstroView 90mm Equatorial Refractor Telescope, Orion SpaceProbe 130 EQ Reflector Telescope

Tomorrow morning: Double star challenge in Coma Berenices

Saturday, December 10
Located on a line from Arcturus in Bootes to alpha Comae Berenices, to Denebola in Leo, above Spica, Jupiter and Vindemiatrix in Virgo, Struve 1657 is a challenge to locate. It is more commonly known at 24 Comae Berenices, a magnitude 5.0 showpiece double with a wide separation of 20.3 arc-seconds. Its deep yellow-orange primary is magnitude 5.1, and its clearly blue companion dimmer at 6.3. As this is not a binary "system,? they are really two individual stars that appear double, by line of sight, with distances of 615 and 2,718 light years, respectively. Still, a great pairing that will satisfy your double star palate.

Skill Level: Intermediate

Suggested Gear: Orion StarSeeker IV 127mm GoTo Mak-Cass Telescope, Orion SkyQuest XT8 Classic Dobsonian Telescope

Tomorrow evening: Planet Mercury

Charts from Starry Night Pro, available from Orion Telescopes & Binoculars. 65 Piscium, Gamma Arietis, Struve 1657 sketches by Jeremy Perez from his webpage "Belt Of Venus." NGC 4565 sketch courtesy of Wes Stone. Melotte 111 drawing from Binocularsky.com. Lunar images from Virtual Moon Atlas. 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 to our Night Sky Tonight post.