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The Night Sky Tonight: May 17 – May 25

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, May 17
By 11:45 tonight Jupiter is up high enough to make it a viable target. The planet's moons are in an interesting configuration with Io above Ganymede, both near Jupiter's disk. Paired farther away on the opposite side of Jupiter are Callisto and Europa, perpendicular in their orientation to the two other moons. The inset also shows the start of Io's shadow transiting the planet's disk, soon to be followed by the moon itself. With a big Moon up tonight this is an excellent target!

Skill Level: Beginner

Suggested Gear: Orion Observer 80ST 80mm Equatorial Refractor Telescope, Orion AstroView 90mm Equatorial Refractor Telescope

Tomorrow Evening: Full Moon

Saturday, May 18
May's Full Moon rises between the constellations Libra and Scorpius, north of east along the horizon. It is 99.77% full and near its average distance at 384,400 km from Earth. Common names for this Full Moon are: Flower Moon, Corn Planting Moon and Milk Moon. As we move now toward the next New Moon, we'll enjoy the last of spring's skies in the north, and Fall in the southern hemisphere.

Skill Level: Beginner

Suggested Gear: Orion Scenix 7x50 Binoculars, Orion AstroView 6 Equatorial Reflector Telescope

Tomorrow Evening: Constellation Virgo

Sunday, May 19
Virgo is the classic spring constellation, tracing to 10th century B.C. Babylonia, where it represented the goddess Shala and an ear of grain. This area of sky is home to the great Virgo Galaxy Cluster, and 11 members of the Messier Catalog. Its brightest star is Spica, one of the 20 brightest stars of the night sky sitting about 250 light years away. The neighboring constellations include (1) Coma Berenices, (2) Bootes, (3) Serpens, (4) Libra, (5) Hydra, (6) Corvus, (7) Crater, (8) Leo.

Skill Level: Beginner

Suggested Gear: Orion 10x50 Binocular Stargazing Kit II, Discover The Stars Beginner's Astronomy Guidebook

Tomorrow Morning: Moon with Jupiter and Red Spot

Monday, May 20
In the early morning hours on the 20th asteroid Massalia is at opposition in eastern Libra, in an easy to locate position near between Lambda (L) and Kappa (K) Librae. Although it will reach magnitude 9.7, this object is faint and will be even more challenging with a big Moon nearby. Two insets are 3 degree finder and 1 degree field of view. The Moon will be very near Jupiter, and near dawn a fine sight with the Great Red Spot in transit.

Skill Level: Beginner

Suggested Gear: Orion 10x50 E-Series Waterproof Astronomy Binoculars, Orion StarBlast 90mm Altazimuth Travel Refractor Telescope

Tomorrow Evening: Splitting Porrima

Tuesday, May 21
The excellent double star Porrima, or Gamma Virginis in Virgo is a nearby double star only 38 light years distant, consisting of nearly identical white main sequence stars forming a binary pair. Easy to identify at a combined magnitude 2.74, the pair have a separation of 2.8 arc-seconds and individual magnitudes of 3.48 and 3.53. This pair was only 0.4 arc-seconds separation in 2006 and will widen to 3.927 by 2030.

Skill Level: Beginner

Suggested Gear: Orion SkyScanner 100mm TableTop Reflector Telescope Kit, Orion StarSeeker IV 127mm GoTo Mak-Cass Telescope Kit

Tomorrow Morning: Moon Targets

Wednesday, May 22
Tonight's waning gibbous Moon is 88.5% illuminated at 391,399 km distance. In 10X binoculars crater Boussingault (1) shows well on the southern limb. 50mm gives crater Atlas (2) plenty of detail, but use 200mm to view the Rimae Atlas (4) inside the crater walls crisscrossing the floor. With 100mm crater Fredholm just outside Mare Crisium shows high walls surrounding its 9 mile diameter circular bowl shape.

Skill Level: Beginner

Suggested Gear: Orion UltraView 10x50 Wide-Angle Binoculars, Orion StarBlast II 4.5 Equatorial Reflector Telescope

Tomorrow Evening: Fine Double Star Theta Virginis

Thursday, May 23
Theta Virginis is a fine multiple star system with four members, three of which are visible. The closest pair is the white primary at magnitude 4.4 and the magnitude 6.83 secondary just 6.8 arc-seconds away at PA 342. The two other members are 71 and 67 arc-seconds away at PA 300 and 297 at magnitudes 10.4 and 9.4. Look closely at the sketch to see the bright A and B components close together.

Skill Level: Beginner

Suggested Gear: Orion SkyQuest XT12i IntelliScope Dobsonian Telescope, Orion StarBlast 6i Intelliscope Reflector Telescope Kit

Tomorrow Morning: Moon Targets

Friday, May 24
Today's waning gibbous Moon is 73.3% illuminated at 398,367 km distance from Earth. 10X binoculars show carter Theophilus (1) with a 61 mile diameter and high walls to 13,300 feet elevation. With 50mm Posidonius (2) and its internal rimae sit right on the Terminator allowing the shadow to put on a show. With 100mm small crater Carrel (3) is an isolated irregular formation in a mountain chain, with high walls and a central mountain. A 200mm instrument gives good views of Rimae Burg's (4) 62 mile length within Lacus Mortis. Great targets!

Skill Level: Beginner

Suggested Gear: Orion Resolux 10x50 Waterproof Astronomy Binoculars, SkyLine 10" Dobsonian Reflector Telescope

Tomorrow Evening: Markarian's Chain in Virgo

Saturday, May 25
Markarian's Chain is one of the great sights visible in amateur telescopes. Sitting in the heart of the Virgo Galaxy Cluster, the chain contains two galaxies in the Messier Catalog, M86 and M84. The chain is named after Benjamin Markarian, the astrophysicist who determined six of the galaxies in the group have common proper motion. In dark skies you may see up to 30 galaxies in the nearby surrounding area including this amazing chain. This sketch was with an 8" Orion XT8.

Skill Level: Beginner

Suggested Gear: Orion SkyQuest XT8 Classic Dobsonian Telescope, Orion SkyQuest XT10 PLUS Dobsonian Reflector Telescope

Tomorrow Morning: Last Quarter Moon Targets

Charts from Starry Night Pro, available from Orion Telescopes & Binoculars. Porrim and Markarian Chains sketches courtesy Jeremy Perez. Theta Virginis sketch from Richard Handy. Lunar photography from Robert Reeves. Other images from Starry Night Pro.

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.