Sky at a Glance 2021 July 24 – 31

Photo showing several constellations that will be along the sky's meridian at about 10 pm this week, including Hercules, Ursa Minor, Ophiuchus and Draco.

This Week’s Sky at a Glance, 2021 July 24 – 31 ~by Curt Nason

Stargazers prefer meridian observing because that is when we should have our best views of objects in a telescope or binoculars. The meridian is the imaginary line running from north to south, separating the sky into eastern and western hemispheres. When stars and planets cross the meridian they are at their highest, 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, so minimal atmosphere means 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 this week we have several prominent constellations near the meridian. 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 several globular clusters itself. Ophiuchus stands on Scorpius, keeping the scorpion underfoot so that it cannot fatally sting Orion again. Scorpius at the meridian is the best time to observe globular clusters M4 and M80, and open clusters M6 and M7.

This Week in the Solar System

Saturday’s sunrise in Moncton is at 5:52 am and sunset will occur at 8:58 pm, giving 15 hours, 6 minutes of daylight (6:00 am and 9:00 pm in Saint John). Next Saturday the Sun will rise at 6:00 am and set at 8:49 pm, giving 14 hours, 49 minutes of daylight (6:07 am and 5:52 pm in Saint John).

The Moon is one day past full this Saturday evening and it is at third quarter next Saturday. Around 11:30 Sunday evening the Moon rises four degrees below Jupiter. Venus moves eastward below the belly of Leo, setting before 10:30 pm. Mars passes to the upper right of Regulus over the week, being closest on Thursday, but binoculars are recommended to pick them out of the twilight as they set before 10 pm. Saturn rises in the east-southeast as Mars is setting, followed by Jupiter 50 minutes later. Telescope users can catch Jupiter’s Red Spot around midnight Wednesday evening. This weekend Mercury rises 50 minutes before sunrise, heading toward superior conjunction on August 1. Look for a few extra meteors rising up from the south on Wednesday evening and overnight as the South Delta Aquariid meteor shower peaks.

Questions? Contact Curt Nason.

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