This Week’s Sky at a Glance, July 22 – July 29 ~by Curt Nason
Many people grew up watching Zenith televisions, which are now made by LG Electronics. Stargazers prefer zenith observing because that is when we should have our best views of objects in a telescope or binoculars. The zenith is the imaginary line running from north to south, separating the sky into eastern and western hemispheres. Objects are at their highest when they cross the zenith, shining through a minimal thickness of atmosphere en route to our eyes. Unstable pockets of atmosphere will distort the light from stars and planets, blurring the view. The less atmosphere light must pass through, the less distortion. Astronomers use the term “seeing” to describe the steadiness of the atmosphere; good seeing means steady air and we can use higher magnification for observing details of the Moon and planets.
Around 10 pm now we have several prominent constellations at the zenith. Moving southward from the North Star we have Ursa Minor or the Little Dipper. A small telescope with good seeing conditions will show the close companion star of Polaris, which is actually a triple star although only two can be seen in a telescope. Heading southward we pass through Draco the Dragon on our way to Hercules. The faintest of the four stars in the dragon’s head is an easy double star to resolve in binoculars. The globular cluster M92 is about halfway between the head and the Keystone asterism of Hercules, and don’t forget M13 along the western side of the Keystone.
Hercules goes head-to-head with Ophiuchus to its south, which contains a few globular clusters itself. Ophiuchus stands on Scorpius, keeping the scorpion underfoot so that it cannot fatally sting Orion again. Scorpius at the zenith is the best time to observe globular clusters M4 and M80, and open clusters M6 and M7. Observing all of these objects near their zenith is much more fun than watching a television of any brand.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 5:50 am and sunset will occur at 9:00 pm, giving 15 hours, 10 minutes of daylight (5:58 am and 9:02 pm in Saint John). Next Saturday the Sun will rise at 5:58 am and set at 8:52 pm, giving 14 hours, 54 minutes of daylight (6:05 am and 8:55 pm in Saint John).
The Moon is new on Sunday and it passes near Jupiter on Friday evening. Mercury is 5 degrees to the upper left of the very slim crescent Moon on Monday, and on Tuesday it is 6 degrees to the lower right and just below dimmer Regulus. Jupiter is best observed in the first hour or so after sunset, before it gets too low in the west for steady viewing. Saturn is well placed for observing all evening between Scorpius and Sagittarius. Venus is the bright Morning Star, rising around 3 am. If you are out past midnight later in the week, keep an eye out for shooting stars from the South Delta Aquariid meteor shower. Mars is in conjunction with the Sun on Wednesday, emerging from the glare of sunrise in mid-September.
Astronomy clubs across the country are participating in a public National Star Party on the evening of July 29. New Brunswick locations are at Mactaquac Provincial Park, the Irving Nature Park in Saint John, and the Moncton High School Observatory.
Questions? Contact Curt Nason.