This Week’s Sky: June 27 – July 4

Mars reverses direction and the Moon wanes to new.

Seronik-LQ Moon

The Moon reaches last-quarter phase on June 27 and is a fine morning-sky telescope target. Courtesy Gary Seronik

All Week

SSW - 1 hr after sunset

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

The evening planet show continues, but there are signs it’s beginning to wind down. One hour after sunset, Jupiter is only about 24 degrees above the west-southwest horizon. Good telescopic views are still possible, but you’ll want to begin your Jupiter session in twilight as soon as you can spot the planet’s magnitude −1.9 disc. At that same time Mars is at the meridian, but even then it’s no higher than Jupiter. The magnitude −1.4 red planet is still a reasonable size (16 arc seconds) and is now far enough past its late-May opposition to display a noticeably gibbous disc. Not far behind Mars is Saturn, which reaches the meridian at 11:20 local daylight time—at the end of astronomical twilight for observers in southernmost Canada. Saturn’s rings are just about as wide open as they can be, which makes the planet an enjoyable sight in telescopes even though at its highest it’s only about 26 degrees above the southern horizon.

June 27

The Moon reaches last-quarter phase today at 2:19 p.m., EDT.

June 30

After travelling westward since April 17, Mars pauses briefly, then begins eastward “direct” motion. It will continue to move in this direction for the next two years.

July 2

Moon and Aldebaran

The crescent Moon and Aldebaran as seen in 10×50 binoculars from Ontario.

This morning the earthlit crescent Moon will rise a about three degrees to the lower left of Aldebaran, the brightest star in the constellation Taurus. The farther east you are, the closer the pair will be; the farther west, the greater the separation.

July 4

New Moon occurs today at 1:01 a.m., EDT.

Today at noon, EDT, the Earth reaches its greatest distance from the Sun (aphelion) when it lies 152,103,776 kilometres from the home star.

Weekend Stargazer

Ophiuchus globulars

Use this chart to locate all seven globular star clusters found in the constellation Ophiuchus. (Click on the image for a full-size version.)

The July 1 – 3 weekend is moon-free, though the nights are still very short (or non-existent) for most Canadians. As a result, deep-sky observing sessions are rather brief. Offsetting this disappointing fact, however, is that pulling an “all-nighter” isn’t terribly taxing. Also, we tend to get clear skies more often at this time of year.

Summer is globular star cluster season. The greatest concentration of these objects is found in the constellations Sagittarius and Ophiuchus—each holds seven Messier globulars. The ones located in the big, sprawling figure of Ophiuchus are easier to catch since most of them are higher in the sky than the Sagittarius clusters.

Start your Ophiuchus globular hunt with M10 and M12—the biggest and brightest of the bunch. You can see them in binoculars without much trouble, though, like most globulars, they really come into their own in a telescope—the bigger the better. Once you catch those two, head east for M14, then seek out M19 and M62, which lie so far south they look as though they belong to neighbouring Scorpius. The most challenging of the Ophiuchus Seven are M9 and M107. They’re fainter and smaller than the rest, so you’ll have to push the magnification a little higher when you search for them.

Try not to rush through this rich collection of clusters—each globular has its own distinct personality. If you look with enough care, you’ll discover that no two are really alike.

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