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This Week’s Sky: May 18 – 25

Saturn reaches opposition and the Moon visits Venus and Jupiter.


Ace U.K. imager Damian Peach recorded this view of Saturn on March 10, 2015. South is up.

All Week

W-45min after sunset

Facing west, 45-minutes after sunset on May 21.

The evening sky is dominated by two bright planets. First to emerge soon after sunset is Venus, shining beacon-like at magnitude –4.2. The planet is positioned smack dab in the middle of Gemini, though only the constellation’s two brightest stars, Castor and Pollux, are visible in twilight. Sharing the same region of sky is Jupiter. It’s a –2.0-magnitude gem situated about 45 degrees above the western horizon as darkness falls. It doesn’t set until around 1:45 a.m., local daylight time, but you’ll want to get your telescopic viewing in as early as possible, when the planet is highest. Last up is Saturn, which clears the eastern horizon at sunset. (For more on Saturn, see Weekend Stargazer below.)

May 21

This evening the Moon will be positioned about 10 degrees to the right of Venus. The pairing will make for an attractive sight in the western sky during twilight.

Lambda Gem occultation

The occultation as viewed in a small telescope at 25×.

Observers from Ontario east will get to see the dark limb of the Moon overtake 3.6-magnitude lambda (λ) Geminorum. The event will be visible in binoculars or small telescopes and occurs at 9:23 p.m., EDT, as seen from Toronto, Ontario. The farther east you are, the darker the sky, but the lower the Moon is at the time of the occultation. Start viewing early though and watch the lunar disc slowly approach the star. And when lambda disappears, it does so instantly — blink and you’ll miss it.

May 22

At 9:35 p.m., EDT, Saturn officially reaches opposition. That means it rises around sunset and is visible all night long.

May 23

Jupiter and Moon

Jupiter and the Moon in the western evening sky.

Tonight it’s Jupiter’s turn to pair up with the Moon. The duo will be closest as they set in the west. The lunar disc lies about 5½ degrees from the giant planet, as seen from Vancouver, British Columbia.

May 25

Today the Moon is at first-quarter phase at 1:19 p.m., EDT. It sets in the evening about five degrees south of Regulus, the brightest star in the constellation Leo.

Weekend Stargazer

Saturn-300× telescope view

This illustration simulates the view of Saturn as it appears at 300× in an 8-inch telescope. (Click on the image for a full-resolution version.)

It seems appropriate on the May 22 – 24 weekend to spend a little quality time with Saturn since it reaches opposition Friday evening. And while it may be visible all night, its low declination means good telescopic views are likely only when the planet is near the meridian. The prime observing window is from about midnight to 2 a.m., local daylight time.

Saturn seems to take magnification better than most other planets — perhaps because of the high-contrast nature of its ring system. This year the rings are tilted favourably, (over 24 degrees from edge-on) making telescopic details such as the Cassini Division easier to see. Notice the difference in tone between the two main rings, and take some time to search for the ghostly C- ring. Another benefit of the rings being presented so open is that the planet appears brighter. Right now it shines at magnitude 0.1, but when the rings are presented edge-on, Saturn dims to magnitude 1.1. Don’t be shy about piling on the power with your telescope, but be mindful of indulging in what is termed “empty magnification.” You’ll know you’ve gone too far when the planet starts to appear fuzzy. A crisp, moderate-magnification view is always preferable to a blurry high-power one.

For more on what the planet has to offer, check out our Guide to Observing Saturn.

At SkyNews we love to read about your experiences and see your photos. You can share them with us by e-mailing dickinsonSkyNews@gmail.com.

Categories: This Week's Sky

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