Thebacha and Wood Buffalo Dark Sky Festival August 2017

This Week’s Sky: May 22 – 29

The Moon visits Venus at dawn and the Beehive at dusk.

Oleg Bouevitch-M51

The Whirlpool Galaxy (M51) is well positioned for evening viewing this week. Photo courtesy Oleg Bouevitch

All Week


The view facing south at roughly 2 a.m., local daylight time.

By the time the sky starts to darken, brilliant Jupiter is already on the meridian and well placed for viewing. The magnitude −2.3 planet is a fine sight even in a small instrument, which will reveal the the main cloud belts and four biggest moons. Indeed, Jupiter’s only telescopic solar-system rivals are Mars (but only every second year when it’s nearest to Earth) and 0.1-magnitude Saturn, which now rises shortly before 10:30 p.m., local daylight time. The famous ringworld culminates around 3 a.m., but due to its location near the Ophiuchus/Sagittarius border, hangs low in the south. Still, no backyard astronomer can resist Saturn’s allure, even when conditions are less than ideal. Last up is the brightest planet of them all, Venus. The magnitude −4.5 morning “star” clears the east horizon around 4 a.m. and can be detected even after sunrise.

May 22

Venus and Moon

The view from the West Coast, facing east 45-minutes before sunrise.

This morning the Earthlit crescent Moon will sit very near the beacon-like planet Venus. West Coast observers will see the pair at their closest when they rise together just three degrees apart in brightening twilight.

May 25

The Moon is new today at 3:44 p.m., EDT.

May 25/26

Shadow transit

The Jupiter shadow transit as seen at high magnification. North is up.

Tonight features a double shadow transit on Jupiter that runs from 10:47 p.m. (May 25) to 12:19 a.m. (May 26) PDT (7:47 p.m. to 9:19 p.m, EDT May 25). The event is visible all across Canada, but the timing is best for observers in Western Canada. The double transit begins when Io’s shadow joins Europa’s, already making its way across the Jovian disc.

May 29

Moon and M44

The Moon and Beehive Cluster (M44) as seen in 10×50 binoculars.

This evening the waxing crescent Moon is positioned less than three degrees south of the Beehive Cluster (M44), in Cancer. The pairing will be a fine binocular sight low in the west as twilight fades. Observers in eastern Canada will see the lunar disc closest to the cluster. By the time darkness falls on the West Coast, the Moon’s eastward motion will have carried it slightly more than a degree farther from the Beehive.

Weekend Stargazer

M51 finderchart

Use this chart to locate the galaxy M51. (Click on the image for a full-size version.)

The moonless evenings of the May 26 – 28 weekend are an invitation for some deep-sky observing. Of course, spring is galaxy season. One of the finest and most famous is the Whirlpool Galaxy, otherwise known as M51. Although it’s located in Canes Venatici, M51 is much easier to find by jumping off from Alkaid—also known as Eta (η) Ursae Majoris, the last star in the handle of the Big Dipper.

M51 is 26 million light-years from Earth—relatively nearby in cosmic terms. Chances are you’ve seen lots of impressive photos of this fine spiral specimen, but don’t let those long-exposure images set your telescopic expectations too high. At magnitude 8.1, the Whirlpool is fairly bright, yet its face-on orientation can make your observation more challenging than you may anticipate.

At nightfall during late spring, M51 is nearly overhead. Under a reasonably dark sky you can spot it with binoculars, while in a modest scope the galaxy appears as a small, round glow with a brighter centre. However, to see the spiral shape that gives the Whirlpool its name, you’ll need more aperture. I’ve detected the arms in an 6-inch, but the subtle spiral form of M51 can only really be described as obvious in a 12-inch or larger instrument.

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Categories: This Week's Sky
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