Night Sky Highlights for July-September 2016
Your best chance to see Mercury this summer will be during the last few days of July and the first few days of August, when it will be low in the west after sunset.
Venus will start to become visible low in the western sky during July, and it will get somewhat higher in August and September. As usual, it will be the brightest object in the night sky other than the Moon.
In July, Mars will be in Libra during July, when it will still be fairly large, and certainly worth checking out with a telescope at medium or high magnification. It will be visible all summer, but getting steadily smaller and dimmer.
The beginning of the summer will also be the best time to view Jupiter, when it will be high in the sky during the evening. It moves lower and further west during the summer, and by September it will be hard to observe in the glow of the evening twilight.
Saturn is well placed for observing during the evenings throughout the summer. From our perspective, its rings are open about as wide as they ever get, so this is a good chance to look for the Cassini division (a dark band separating the inner and outer portions of the rings). Though a telescope of moderate size, several of its moons should also be visible.
Perseid Meteor Shower
Peaking on the night of August 12-13
This is always a good summertime meteor shower, but moonlight will be a bit of a problem this year. On the peak night, a waxing gibbous Moon will be in the sky throughout the evening, so the best time to look will be in the early morning hours, after the Moon has set. Some Perseids can be seen for many days before and after the peak, however, and it might be advantageous to look on the nights before August 12, when the Moon will be smaller and set sooner.
Deep Sky Objects
On summer evenings, the brightest parts of the Milky Way stretch across the sky, from Perseus in the northeast to Sagittarius in the south. There are countless open clusters, globular clusters, and nebulae to be seen. Here are just a few of the sights worth exploring.
Messier 4 and 80
Globular clusters in Scorpius
These two globulars have very different appearances in a telescope. M4 is just about 1 degree to the west of first magnitude Antares, and it is very loosely structured. M80 is about 4 degrees northwest of Antares. It is smaller and very condensed, with a bright center and individual stars resolved around the edges.
Messier 11, the Wild Duck Cluster
Open cluster in Scutum
This is one of the richest open clusters in the sky, and contains more than 1000 stars. Someone apparently thought it looked like a flock of wild ducks in flight, but not many who look at it through the eyepiece get that impression. Still, it is a spectacular sight under dark skies.
Messier 29 and 39
Open clusters in Cygnus
These two open clusters are quite different in size and shape. M29 is a small but distinct cluster of about a dozen stars, approximately 12′ across. M39 contains many more stars and is much larger, at least 30′ across.
Messier 8, the Lagoon Nebula
Diffuse nebula in Sagittarius
M8 is one of the few nebulae visible to the naked eye, a small hazy patch above the spout of the Sagittarius “teapot” shape. It is a fine object to view through binoculars, and very impressive through a telescope. It includes the open star cluster NGC 6630.
Messier 16, the Eagle Nebula
Diffuse nebula in Serpens
Like the Lagoon Nebula, this object also consists of an emission nebula and an open cluster. Compared to the Lagoon, however, the nebulosity is dimmer and harder to see unless you have a good dark sky. It looks better though larger telescopes, and if you ever have the chance to observe it through a big Dobsonian scope, be sure to take a good long look.
Messier 17, the Swan Nebula
Diffuse nebula in Sagittarius
M17 is a very bright emission nebula that can be seen quite easily in binoculars. Through a telescope, it has the shape of a swan in profile. However, the exact shape varies with one’s telescope, viewing conditions, and imagination, and this nebula has also been called the Omega Nebula, the Horseshoe Nebula, and the Check-Mark Nebula. Take your pick.
Messier 27, the Dumbbell Nebula
Planetary nebula in Vulpecula
One of the biggest and brightest examples of a planetary nebula, the Dumbbell’s shape can easily be seen in even a small telescope. In a large telescope with high magnification, it is an amazing sight, with many dim stars scattered across the surface of the nebula.
NGC 7000, the North America Nebula
Diffuse nebula in Cygnus
In photographs, this nebula has the shape of the North American continent, and many of its features can be seen visually through a rich-field telescope with careful observation. This nebula and the many stars in its vicinity fill a large area of sky, and it can be seen with the naked eye, just a few degrees to the east of first-magnitude Deneb.
Dark nebula in Cygnus
This dark nebula is strictly a naked-eye or binocular object. It appears as a long dark finger intruding into the Milky Way, about 7 degrees to the north-northeast of Deneb. Phil Harrington estimates that it is a full 10 degrees long and 3 degrees wide. Look for it on a clear dark summer night when the Milky Way is high overhead.