Jasper Dark Sky Festival

This Week’s Sky: July 25 – August 1

Aldebaran greets the Moon while Mercury and Venus hang low.

Cygnus Milky Way

Some of the richest parts of the Milky Way lie within the Summer Triangle, outlined by the stars Deneb, Altair and Vega. Courtesy Gary Seronik

All Week

SSW-1hr after sunset

The view facing south-southwest, one hour after sunset.

There’s a veritable planetfest in this week’s evening sky—but you can enjoy it only if you have an unobstructed western horizon. Jupiter, Mars and Saturn are easy to identify in fading twilight, as they form an attractive string of lights along the horizon, from south to west. All three are bright: Jupiter is magnitude –1.8; Mars is magnitude –0.9; and Saturn is magnitude 0.3. And you can add two more targets to your tally if you to start early and scan the west horizon with your binoculars. With a little luck you might sweep up Mercury and Venus. At magnitude –3.9, Venus will be the easier catch of the two. You should be able to spot it moments after the sun goes down, when the planet has an elevation of about 5 degrees. Venus sets a bit north of due west, 45 minutes after the Sun. Somewhat higher, but a lot fainter, is Mercury. It shines at magnitude –0.3 and dips below the horizon one hour after the Sun. Both inner planets are at the start of their evening apparitions, so if you don’t pull off a sighting under this week’s challenging conditions, don’t despair—the situation will gradually improve.

July 26

The Moon reaches last-quarter phase today at 5 p.m., EDT.

July 28/29

The Southern Delta Aquarid meteor shower peaks tonight. It’s a modest display that, under ideal conditions, produces some 20 meteors per hour, radiating from a point roughly 15 degrees north of the first-magnitude star Fomalhaut, which lies due south a little before 4 a.m., local daylight time.

July 29

Moon and Aldebaran

The Moon and Aldebaran as seen in 10×50 binoculars from Calgary, Alberta.

This morning, the Moon and Aldebaran, the brightest star in Taurus, have a very close encounter. How close depends on where you live. Observers in the prairie provinces are best situated as the Moon is nearest Aldebaran at 4:33 a.m., MDT (6:33 a.m., EDT). From Calgary, the lunar disc will pass only ¼ degree south of the distinctly reddish, 1st-magnitude star. The close encounter should be a lovely sight in binoculars, a small telescope or even with your bare eyes.

Weekend Stargazer

Dark Nebula chart

Use this chart to identify the Northern Coal Sack and Barnard’s E. Click on the image for a full-size view. Base chart courtesy Glenn LeDrew

The Moon is largely out of the picture over the July 29 – 31 weekend, so deep-sky observers can enjoy one of only a handful of moonless summer weekends. For observers at the latitude of Edmonton, Alberta (54 degrees north), this is the first summer weekend that features any astronomical darkness! One class of deep-sky object demanding moonless country skies is the so-called dark nebulas. Indeed, if you can’t see the Milky Way really well from your observing site, these opaque interstellar clouds of dust and gas are impossible to spot.

When you look along the band of the Milky Way, you’ll notice numerous dark rifts and patches. One conspicuous area, known as the Northern Coal Sack, hides in the celestial weeds southeast of 1.2-magnitude Deneb, the brightest star in Cygnus. This feature is part of a much larger dark assemblage known as the Great Rift, which bisects the summer Milky Way for much of its length.

Another well-known dark nebula is Barnard’s E, located a few degrees northwest of 0.9-magnitude Altair, the brightest star in Aquila. Use your binoculars (or a small, wide-field telescope) to detect a ragged, E-shaped blackish blob about one degree due west of 2.7-magnitude gamma (γ) Aquilae. Observing the ghostly “E” takes some getting used to, but once you train your eye to look for an absence of starlight, you’ll be surprised at the number of other dark nebulas you can pick up with binoculars.

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

Categories: This Week's Sky
Khan Scope
Lightrack II Travel Mount for Astrophotographers
TAWBAS Dark Sky Festival
LX200 Sale!
iOptron Tri Pier 10% off
Canadian Telescopes
Give the Gift of SkyNews