Time to Observe Planets in the Night Sky

Jupiter is the very bright object in the western sky after darkness falls. Grab your telescope and take a look early — it sets before 1 am. Even a small telescope can show interesting events among Jupiter’s four bright Galilean Satellites named Io, Europa, Callisto, and Ganymede (in order of distance from Jupiter). Below are the best Jupiter moon events this week (all times in EDT). (Southern hemisphere observers should swap left and right in the notes below.)

On Wed, Jun 22 at 9:11 pm, Io disappears behind Jupiter’s right edge. On Thursday night, Jun 23 at 9:48 pm, Io’s shadow completes a transit started in daylight. Ganymede’s shadow transits on Friday night, Jun 24, from 11:37 pm until Jupiter sets at 12:42 am. Europa’s shadow transits on Saturday night, Jun 25, from 11:41 pm until Jupiter sets. Get out your scope, big or small, and try them! (Remember that your telescope may reverse or flip the view.)

The Great Red Spot (GRS) on Jupiter can also be observed in a decent backyard telescope, if you know when to look. Great Red Spot transits take about three hours to complete. Here are the eastern daylight times of the GRS transits visible in the GTA this week, given for the midway point (i.e., 90 minutes into it): Tue, Jun 21 at 10:14 pm, Thu, Jun 23 at 11:53 pm, and Sun, Jun 26 at 9:24 pm.

Bright reddish Mars and dimmer, yellowish Saturn continue to shine together from dusk until about 3 am, and both are terrific telescope targets. As the sky gets dark, Mars is due south, and not too high in the sky (about 25° up). Saturn is about two outstretched fist diameters to Mars’ lower left. Around 11 pm, they reach their highest point above the southern horizon and then they begin to sink into the west well before dawn. Saturn sets about 4:30 am. I’ll post a diagram here. If you check out Saturn in your telescope, look for some of its brighter moons, especially Titan. They can be found above, below, or to either side of the planet — usually within 5 or 6 ring diameters of the planet.

If you missed last week’s tour of the bright June stars, it’s here.


Iridium flares are glints of sunlight off of the flat reflecting sides of one of the satellites that comprise the Iridium pager and sat-phone network. The flares occur before dawn and after dusk, when the satellite passing overhead is still illuminated by the Sun, which is below the horizon for observers on the ground. The duration and brightness depend on the angles between the observer, the satellite, and the Sun. For even more info about Iridium Flares and the space station, see an article that I wrote here. Using an accurate clock, go outside a few minutes ahead and look in the direction indicated. You should first see the dim Iridium satellite moving quickly across the sky, and then it will rapidly brighten for 3 to 8 seconds, and fade out. Truly spectacular! The more negative the Magnitude number, the brighter. The larger the Alt. number, the higher up it is! (The horizon is 0°, and 90° is straight up, so 55° is a bit higher than halfway between the horizon and zenith.) These data are adapted from www.heavens-above.com. To get your own schedule, enter your location in their website.

The ISS (International Space Station) is also visible at times, gliding silently overhead. If you enter your location in the www.heavens-above.com website, you will get a list of them for wherever you might be.)

Keep looking up to enjoy the sky! I love getting questions so, if you have any, send me a note.

Stargazing News for this week (from June 19th) by Chris Vaughan. (Feel free to pass this along to friends and send me your comments, questions, and suggested topics.) I post these with photos at http://astrogeoguy.tumblr.com/ where the old editions are archived. You can also follow me on Twitter as @astrogeoguy! All times mentioned are in Eastern Daylight Time. Please click this MailChimp link to subscribe to these emails. If you are a teacher interested in a guided field trip to the David Dunlap Observatory, details are available at www.astrogeo.ca.

My latest column for Space.com, about how to take astro-images of the Moon, bright stars, and planets with your smartphone, went live on Friday. The link is here. In future columns, I’ll cover taking advanced pictures with your phone.

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