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The Night Sky Tonight: September 18 – October 1

By Mark Wagner

Mark Wagner brings us highlights of what's happening in the sky each night this week. Click on each image to enlarge the view. Happy gazing!

Friday, September 18
Get outside before sunup and look for constellation Gemini, the Twins. The (A) Alpha star is Castor, magnitude 1.56 and 52 light years from us. Pollux is the other "twin" just below at magnitude 1.15 at 34 light years. Bordering constellations include (1) Auriga, (2) Lynx, (3) Cancer, (4) Canis Minor, (5) Monoceros, (6) Orion and (7) Taurus. Gemini is a member of the Zodiac, so the Moon and planets pass through it boundary, as Venus did a short time ago. Gemini contains fine double stars, opens clusters and planetary nebulae that we'll visit in the next two weeks.

Skill Level: Beginner

Suggested Gear: Orion 2x54 Ultra Wide Angle Binoculars, Orion 4x21 Super-Wide Angle Binoculars

Tomorrow Evening: Saturn And Its Moons

Saturday, September 19
Saturn is due south at 21:00 tonight, and a great target for its beautiful deeply tilted rings and five bright moons. To its west is Jupiter, the two planets slowly closing toward a spectacular conjunction November 18th when the two planets join the Moon. Tonight see if you can identify Saturn's bright moons Titan, Dione, Enceladus, Tethys and Rhea. Titan is the brightest and the second largest of our solar system's moons is well separated from the others, all ranging in magnitude from 8.6 to Enceladus' 11.99.

Skill Level: Beginner

Suggested Gear: Orion StarMax 90mm TableTop Maksutov-Cassegrain Telescope, Orion SkyQuest XT6 Classic Dobsonian Telescope

Tomorrow Morning: Gemini's Messier Cluster

Sunday, September 20
Early risers are enjoying fine naked-eye views of Venus as it moves through constellation Cancer. Mornings also offer binocular and telescopic views of Gemini's bright open cluster M35 as well. Follow the Twins' chain of stars from (A) Castor to the indicated spot. Do you see it as a fuzzy spot in your binoculars? If you use a telescope, try too for the much more distant open cluster NGC 2158, visible in this inset as the fuzzy spot to the right. M35 is a bright magnitude 5.5 at a distance of 3,870 light years, covering nearly the size of a Full Moon.

Skill Level: Beginner

Suggested Gear: Orion GiantView ED 20x80 Waterproof Astronomy Binoculars, Orion GiantView BT-70 45-degree Binocular Telescope

Tomorrow Evening: Occultation of Beta Scorpii

Monday, September 21
Have you ever watched a bright star occultation? Beta Scorpii is naked-eye at magnitude 2.6 star at the northwest of the familiar constellation figure. The Moon will cover it at 23:27:40 U.T. low in the southwest. Visible from the United States, Mexico and Central America, check your local time when the star blinks out on the dark limb of the Moon:

Skill Level: Beginner

Suggested Gear: Orion SkyQuest XT8 PLUS Dobsonian Reflector Telescope, Orion StarSeeker IV 127mm GoTo Mak-Cass without Controller

Tomorrow Evening: Double Star Castor In Gemini

Tuesday, September 22
Here's an easy to split easy to find double star to view in your telescope this morning. Castor is the (A) Alpha star of constellation Gemini, and the western of the "twins" including Pollux. Its nature as a double star was discovered by James Pound in 1718. It primary member is magnitude 1.93 and secondary with 5.3 arc-seconds separation at magnitude 2.97. The pair are a true binary at a distance of nearly 51 light years. If you view it, post your impression of its stars' colors, and how easy or difficult you found seeing both members.

Skill Level: Beginner

Suggested Gear: Orion StarBlast 102mm Altazimuth Travel Refractor Telescope, Orion AstroView 120ST Equatorial Refractor Telescope

Tomorrow Evening: First Quarter Moon Targets


Wednesday, September 23
Tonight's First Quarter Moon is 50.7% illuminated at 375,873 km distance. A 10X Binocular gives excellent view of (1) Montes Caucasus on the northern border of Mare Serenitatis. With 50mm craters (2) Eudoxus and (2) Aristoteles are an excellent pair together north of the aforementioned Mare. West of Eudoxus is little (3) Crater Lamech showing high walls and a flat floor in its 8 mile diameter. Using 200mm (4) Crater Linne is isolated in Mare Serenitatis, a two miles diameter bowl surrounded by clear material.


Skill Level: Beginner

Suggested Gear: Orion Scenix 10x50 Wide-Angle Binoculars, Orion StarSeeker IV 150mm GoTo Reflector without Controller

Tomorrow Evening: Moon, Jupiter And Saturn Together

Thursday, September 24
Tonight step outside and note the Moon, 7.6 days old at waxing gibbous, directly over the southern horizon at 20:00 PDT. Above and trailing it are the two giant planets Jupiter shining at magnitude -2.39 and Saturn at magnitude 0.43. All are nicely set near the familiar asterism of the Teapot, and lesser known Teaspoon in Sagittarius. Tomorrow night the Moon will pass both planets to their east, entering constellation Capricornus.

Skill Level: Beginner

Suggested Gear: Orion GoScope 80mm TableTop Refractor Telescope, Orion StarBlast 114mm AutoTracker Reflector Telescope

Tomorrow Morning: Eskimo Nebula

Friday, September 25
One of the wonderful bright non-Messier targets available to small telescopes is NGC 2392, the Eskimo Nebula in Gemini. Easy to locate along the familiar stick-figure, this planetary nebula is detail rich and obvious in the eyepiece. At first, you'll find it appearing as a fuzzy star using low power. With sufficient magnification you'll see a ring structure and central star. Magnitude 9.9 and 15" size, it sits approximately 6,500 light years distant. Discovered by Sir William Herschel in 1787, it is also known as the Clown Face Nebula.

Skill Level: Beginner

Suggested Gear: Orion StarBlast 6 Astro Reflector Telescope, Orion GoScope 80mm Backpack Refractor Telescope Kit

Tomorrow Evening: Waxing Gibbous Moon Targets

Saturday, September 26
Tonight's waxing gibbous Moon is 80% illuminated at 9.67 days and 389,892 km distance. Use a 10X pair of binoculars to ferret out (1) Mare Insularum right on the Terminator. Only its eastern shore will be visible. With a 50mm famous crater (2) Copernicus is full of detail within its 56 mile diameter. Can you see the crater's hexagonal shape? Spend time here, it is a splendid area. To its south, with 100mm instruments crater (3) Fauth, nicknamed "Hole Of Lock" for obvious reasons. 7 miles diameter and attached for Fauth A. Finally, with 200mm look for the volcanic shield dome (4) Hortensius 3 in Mare Insularum.

Skill Level: Beginner

Suggested Gear: Orion StarBlast 90mm Altazimuth Travel Refractor Telescope, Orion SkyQuest XT8 PLUS Dobsonian Reflector Telescope

Tomorrow Morning: Colored Double Star 20 Geminorum

Sunday, September 27
Here is a fine colored double star that is easy to locate and fine for small telescopes. 20 Geminorum is located just 2 degrees west of (G) Gamma Geminorum, shining at magnitude 6.25 from a distance of 261 light years. Its primary member is yellow at magnitude 6.31 with a white companion magnitude 6.88 with 20.7 arc-seconds separation. Colorful double stars vary greatly; this color combination is less common, and very pleasing.

Skill Level: Beginner

Suggested Gear: Orion GoScope III 70mm Refractor Travel Telescope Kit, Orion SpaceProbe II 76mm Altazimuth Reflector Telescope Kit

Tomorrow Evening: Mars In The Evening

Monday, September 28
Mars is now rising early in the evening sky! Opposition occurs in only a few weeks on October 14, so the Red Planet is about as large as it will be for the next two years. Have you been watching it? Have you noticed its recent retrograde motion, looking as if it changed directions and is moving back along the Ecliptic? Shining at magnitude -2.45, it has moved ahead of Jupiter among out solar system's brightest objects, behind only the Sun, Moon and Venus. Its current size is 22 arc-seconds at a distance of 0.41 A.U. If you've been viewing it, post what you see here.

Skill Level: Beginner

Suggested Gear: Orion StarSeeker IV 102mm GoTo Mak-Cass without Controller, Orion CC6 6" Classical Cassegrain Telescope

Tomorrow Morning: Carbon Star TU Geminorum

Tuesday, September 29
If you like colored stars, Tu Geminorum is a fine choice in a terrific field. Start by finding the big and bright open cluster M35, off the western foot of Gemini. In your finder you can note 1 Gem, at magnitude 4.5, a spectrographic double star. Nearly opposite it across M35 is Tu Geminorum, a ruddy carbon star and semi-regular variable with a period of 217 days from magnitude 6.88 to 8.0. Enjoy its color and see if you can estimate its current magnitude.

Skill Level: Intermediate

Suggested Gear: Orion Carbon Fiber ED66 CF Refractor & Tritech CFX Tripod, Orion ED80T CF Triplet Apochromatic Refractor Telescope

Tomorrow Evening: Jupiter Show!

Wednesday, September 30
Have your telescope at the ready as night falls tonight, with a great show on Jupiter in progress. As soon as you can find Jupiter start looking for Callisto's shadow transit, which began before sunset. As it approaches egress, at approximately 20:58 PDT look for the Great Red Spot (GRS) turning into view while Io pops out of the darkness of eclipse. Look for detail in the belts as well as there has been a great deal of turbulence in evidence this year. Callisto's shadow will leave the disk of Jupiter at 22:47.

Skill Level: Beginner

Suggested Gear: Orion EON 130mm ED Triplet Apochromatic Refractor Telescope, Orion EON 104mm ED-X2 f/6.25 Triplet Apo Refractor Telescope

Tomorrow Morning: Regulus Conjunction With Venus, Full Moon

Thursday, October 1
Treat yourself to an astronomical event that only requires your eyes, and an early start. Venus conjuncts with Leo's first magnitude alpha star Regulus before sunrise, separated by less than two degrees fitting easily into a pair of binoculars. In a telescope Venus will show as a nearly full disk, shining at magnitude -4.08. Tonight look again at the eastern horizon to see the first Full Moon of fall in the northern hemisphere, or springtime to southern hemisphere residents.

Skill Level: Beginner

Suggested Gear: Orion ShoreView Pro II 8x42 ED Waterproof Binoculars, Orion UltraView 10x50 Wide-Angle Binoculars

Tomorrow Evening: Moon Conjuncts With Mars

Charts from Starry Night Pro. M35, Eskimo Nebula and Castor sketches by Jeremy Perez. Lunar images from NASA.

Mark Wagner is a lifelong 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.