Five planets and a first-quarter Moon adorn the evening sky.
Our five-planet evenings are coming to an end. Mercury (planet #5 in our tally) is going to be a challenge to sight even if you use binoculars and have an unobstructed west horizon. The 0.8-magnitude planet is wrapping up its current apparition and sets one hour after the Sun. Fortunately, the solar system’s other offerings are much easier to enjoy. Venus is the reigning evening “star” and gleams at magnitude –4.2, due west at dusk. Next in line is Jupiter, shining at magnitude –2.2 and already past the meridian at sundown. By midnight, 0.1-magnitude Saturn is culminating and its magnificent rings await telescopic inspection. Bringing up the rear is the summer’s solar-system show stopper: Mars. It rises around 10 p.m., local daylight time and hits the meridian a little after 2 a.m. The red planet reaches opposition next week, and, at magnitude –2.7, noticeably outshines Jupiter. For more on observing Jupiter, Saturn and Mars, see Weekend Stargazer, below.
The Moon reaches first-quarter phase today at 3:52 p.m., EDT.
This evening the waxing gibbous Moon is positioned just three degrees north of brilliant Jupiter. The pairing will be a fine naked-eye sight and a treat in binoculars. The Moon will be closest to Jupiter at around 11:15 p.m., EDT.
Moonlight intrudes into the prime, late-night observing hours over the July 20 – 22 weekend. Luckily, there’s still plenty to see, including the three most rewarding telescopic planets.
As early as possible, aim your scope at Jupiter. Big Jove is past its prime, and the sooner you can spot it, the higher in the sky it will be. Higher is always better when it comes to increasing your chances of experiencing steady seeing conditions. Conversely, the lower your target is, the thicker the cross-section of atmosphere you must view through, and the less satisfying the telescopic image is likely to be. In the case of Jupiter, you don’t have to wait until dark—the planet shows up well at dusk, soon after sunset. I find the subtle colouring of Jupiter’s belts and, when it’s visible, the Great Red Spot, are more pronounced when contrasted against a deep blue, twilight sky.
Next, shift your attention eastward to catch Saturn. These nights, its magnificent rings are on full display, just one degree shy of their maximum tilt. This makes the famous Cassini division (the dark gap separating the two brightest rings) easier to sight. Like Jupiter, Saturn is handicapped by its low elevation, so you want to be sure to observe it at its highest. This weekend, the wondrous ring world peaks at around 11:45 p.m., local daylight time. Even then, Saturn hangs low in the south. Such is the nature of planetary observing during Canadian summers—the weather is usually favourable, but it’s the most southerly region of the ecliptic that culminates in the middle of the night.
Finally, there’s Mars. Normally, right about now the excitement would be mounting dramatically as we count down to the red planet’s most favourable opposition since 2003. But the situation is far from normal. Yes, the Martian disc this weekend spans 23.7 arc seconds, which is only a hair shy of the maximum it will attain during closest approach on July 31; but Mars, too, is mired in the basement of the zodiac. Worse, an ill-timed, globe-enshrouding dust storm is conspiring to obscure virtually all Martian surface markings, no matter how powerful the telescope. All we can do is watch, wait, and hope that the dust settles soon.
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