Thebacha and Wood Buffalo Dark Sky Festival August 2017

This Week’s Sky: April 24 – May 1

The Moon eclipses Aldebaran in daylight, and Venus gleams in the morning sky.


Lynn Hilborn, of Grafton, Ontario, captured this superb view of the Trio in Leo galaxy group. The galaxies are (from left to right), edge-on spiral NGC3628, spiral M65 and barred spiral M66. The Trio are well placed for viewing this week.

All Week

South, 1hr before sunrise

The view facing south, one hour before sunrise.

As dusk fades this week, two planets vie for attention—one on its way out, the other in its prime. The one that’s losing a battle with twilight is Mars. The red planet was in its full glory a year ago when it was nearing opposition, now it’s merely a 1.6-magnitude speck that’s becoming increasingly difficult to spot, low in the west. Thankfully, we have Jupiter. The magnitude –2.4 beacon is well up as darkness falls and reaches the meridian—when it’s best in telescopes—at midnight, local daylight time. Next to appear is Saturn, which clears the southeast horizon around 12:30 a.m. Even at the meridian, the 0.3-magnitude ringed planet is quite low, achieving a maximum altitude of around 20+ degrees at roughly 5 a.m. Saturn’s actual height depends on your latitude. For example, from Edmonton, Alberta, the planet only climbs 14 degrees above the horizon, making crisp telescopic views a challenge. Finally, Venus rises like an airplane landing light in the east a little before 5 a.m. You simply can’t miss the magnitude –4.7 morning “star” even if you wait until a few minutes before sunrise to look for it. It’s just that bright.

April 26

New Moon occurs this morning at 8:16 a.m., EDT.

April 28

Moon and Aldebaran

Mere moments before the Aldebaran occultation as seen in a small telescope at 30×.

Observers in southern Saskatchewan and Manitoba, and in Ontario, Quebec, and the Maritimes, will get a chance to see the dark limb of the crescent Moon occult Aldebaran in daylight. From Regina, Saskatchewan, the occultation starts at 10:44 a.m., CST; from Winnipeg, Manitoba, at 11:37 a.m., CDT; from Toronto, Ontario at 12:28 p.m., EDT; from Montreal, Quebec, at 12:37 p.m., EDT; and from Halifax, Nova Scotia, at 1:48 p.m., ADT. Aldebaran is bright enough to be visible in daylight even in a small telescope, provided it’s sharply focused. Having the Moon nearby makes it easier to locate the star. Just be sure to leave yourself plenty of time before the event begins to set up your scope and get ready.

April 30

45 minutes before sunrise

Facing east, 45 minutes before sunrise.

This morning Venus reaches its greatest brilliancy in the dawn sky, shining at magnitude –4.7. It will remain at that brightness until mid-May, when it dims imperceptibly to magnitude –4.6.

May 1

West, 45 min after sunset

The view facing west, 45 minutes after sunset.

Look to the west during evening twilight to see Mars sitting roughly seven degrees to the right of Aldebaran. Both will be quite low, so choose an observing spot with a relatively unobstructed horizon.

Weekend Stargazer

Leo Trio

Three galaxies lie in the same finder field as theta (θ) Leonis.

Mostly moonless nights over the April 28 – 30 weekend make this prime time for galaxy hunting. At nightfall, both Leo and Virgo are high in the south, and they’re chock-a-block with distant “island universes.” One of my favourite galaxy groupings is the Trio in Leo, which includes M65, M66 and NGC3628. To see them well, though, you’ll need a dark sky—the feeble glow from distant galaxies doesn’t stand up well against a wash of city light pollution.

The Trio in Leo are easy to locate. Start at 3.3-magnitude theta (θ) Leonis, then head south-southeast about 2½°. Of the three galaxies, M65 and M66 are the brightest, at magnitudes 10.1 and 9.6, respectively. Indeed, I’ve even glimpsed them in binoculars. But to add 10.4-magnitude NGC3628, you’ll need a telescope. The big edge-on appears dimmer than its magnitude indicates, yet a six-inch instrument will show it quite readily to complete the trio. If you have good sky conditions, you can probably succeed with something smaller.

There are several dozen galaxies in the region within the grasp of a modest telescope—these three in Leo are simply among the best. Get out your star atlas and spend a pleasant spring evening galaxy hopping.

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Categories: This Week's Sky
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