Wonders of the Summer Sky
by Tom Seymour
Picture a clear summer night, with our own galaxy, the Milky Way, describing a sparkling path across the pitch-black sky. Individual stars stand out from the rest perhaps because of their brightness or maybe because of their striking color. And then we have those multitudes of shapes made by “connecting the dots” and forming imagined patterns.
Pareidolia, the phenomenon responsible for people seeing images in clouds and the man in the moon, also works for us as we try and visualize the various geometric, random and fanciful shapes we see in the night sky.
Some of these shapes are indeed, constellations. In 1930, the International Astronomical Union chose 88 official constellations. These include every star in the heavens. And while a star may belong within the boundaries of a certain constellation, it may not be part of any recognizable pattern.
Often, though, certain stars form recognizable shapes other than those of the official constellations. These are called “asterisms,” and many of these are more universally recognized than are some of the more obscure constellations. Prominent among these are The Big Dipper, an asterism in Ursa Major, The Summer Triangle, formed of stars belonging to three different constellations and The Northern Cross, a group of stars in the constellation Cygnus, The Swan.
All we really need to begin experiencing the wonders of the night sky are our eyes. Without any sort of optical assistance, we can easily see the constellations, asterisms, planets and even some deep-space objects such as the Andromeda Galaxy.
In fact, naked-eye viewing may prove the best way to become conversant with the night sky. Learning a certain part of the sky by heart and then going on to another, forms a sky knowledge that can then be transferred to more in-depth viewing, with either binoculars or telescope.
It helps to have some kind of guide, perhaps a book on constellations or better yet, a sky atlas. To truly become conversant and learn your way around from one point in the sky to another, a sky atlas has no peers.
Before getting started, though, here are some preliminary procedures to consider. Standing still and looking straight up leads to stiff necks and muscle aches. So first and foremost, get comfortable. A folding lawn or beach chair makes it possible to stare up in the sky for a long length of time in total comfort.
Also, even though it is August, nights here in Maine can see chilly temperatures. So bring a sweater or light jacket. And don’t forget insect repellent. Mosquitoes can ruin an otherwise fun-filled evening of sky watching.
Night vision comes into play now. Set up your sky watching session away from artificial lights. Streetlights, porch lights and the like ruin night vision and also, dilute the clarity of the sky.
That said, night vision requires some time to take effect. Within 10 minutes of gazing into a dark sky, many more stars will appear than what you initially saw. And after 30 minutes, many multitudes of stars become visible, some of relatively low magnitude, or brightness.
So after waiting the prerequisite time to develop proper night vision, it would be a shame to lose it. And that can happen in an instant. All it needs is a bright light and night vision goes back to square one. Which explains why anything but red light is banned at organized star parties. Red light does not interfere with night vision. Red lights, specially designed for nighttime use, are available from astronomy outlets. But you can easily make a perfectly useable red light by taping a sheet of red cellophane over a flashlight lens.
By the way, if you see a strange, or out-of-place “star” sailing through the sky, especially around dusk, you are probably watching a satellite. Among these, the International Space Station is widely viewed at sunset, when light from the just-lowered sun shines on it. To find more about when and where the ISS travels, go to: SkyandTelescope.com/satellites. Also see spaceweather.com/flybys/.Milky Way
The Summer Milky Way is a thing of spectacular beauty. Sadly, many areas of the country have so much light pollution from artificial lighting that this trademark sight is no longer visible. This is true for about 60 percent of the country. Not so for most of Maine, however. In fact, Maine, with the darkest skies east of the Mississippi, stands among the states with the darkest skies around and of that, Acadia National Park has gained considerable fame as a premier dark sky site.
In fact, Acadia hosts the annual The Acadia Night Sky Festival, slated for September 13-17 of this year. For more information go to www.acadianightskyfestival.com.
The National Park Service recognizes the value of dark skies and rangers work with volunteers in presenting sky-watching programs. Also, in keeping with the effort to thwart light pollution, artificial lighting in Acadia is positioned so that it causes little or no adverse effects.
So whether in Acadia or elsewhere in Maine, anywhere where dark skies prevail, look for the silvery sheen of The Milky Way stretching from south to north. And as you observe, remember that a significant number of Americans have never seen the Milky Way.
Considering Milky Way observing, now is a good time to mention the value of binoculars. These offer a wide-field view and enough magnification to present breathtaking views of deep-sky objects, the star fields of The Milky Way and even selected double stars. Double stars, by the way are either two stars that are gravitationally connected and travel through space together, or two stars that have no physical relationship with each other, but appear as doubles because of our position in viewing them. These latter are known as optical doubles.
So get out those binoculars. Any binoculars are better than none, but the tiny opera-glass types are of little value. Most full-size binoculars can do the trick for amateur observers. Of these, 10 X 50 is the best choice for the casual astronomer. These numbers, by the way refer first to magnification factor and second, to the diameter of the objective lens, in millimeters. The second set of numbers on binoculars refers to field of view. The larger the numbers, the greater the field of view.
Now, with proper night vision, a comfortable chair and a set of binoculars steadily braced with resting elbows, take a tour of The Milky Way. Spend time as you feel the desire. Soon, lots of amazing shapes will take place, asterisms that have not yet been categorized will pop into view.
A person could easily spend an entire summer’s evening navigating the star fields of The Milky Way.
In August, the constellation Cygnus, home to The Northern Cross, sits nearly overhead. Given the apparent movement of the stars, Cygnus is best observed around 10 pm in early August and shortly after dusk in late August.
After looking up, spot Cygnus by first identifying the Northern Cross. Deneb, the star marking the head of the cross, is also the tail of Cygnus, The Swan. After becoming familiar with the cross, try and imagine a reverse image and that is when the swan shape becomes apparent.
Slightly west of Deneb lies the triple star Omicron, or 31 Cygni. Slowly sweep along with binoculars and look for golden, 31 Cygni and its bluish-white companion, 30 Cygni. Considerably dimmer but also visible in binoculars, is a third star, this one harder to see.
Also nearly overhead and slightly west of Cygnus, lies the constellation Hercules. Within this grouping of relatively dim stars, find the asterism known as The Keystone. This really does resemble a keystone, or capstone, used in building arches.
And in The Keystone, we find the famous M13, The Hercules Cluster, a globular (globe-shaped) star cluster consisting of 500,000 stars. This is barely visible to the naked eye and easily viewed in binoculars. It resembles a large, fuzzy, gauzy star.
To find M13, draw an imaginary line between the two western stars of The Keystone and look for the cluster about one-third of the way down between the two.
On the night of August 11 and continuing into the early morning of August 12, the annual Perseid Meteor Shower will reach its peak. While viewers can see the occasional meteor the night before and the night after, best viewing begins around 11 pm on Saturday night.
So-called because it appears to emanate from the constellation Perseus, low in the northern sky, this shower is one of the most popular not because of the number of meteors seen (one or two per minute after midnight), but because it occurs in summer, when temperatures are conducive to extended periods of sky watching.
A waning crescent moon arising around 1 or 2 am will shed only dim light and won’t constitute much of a light-pollution problem. For more on this, go to www.skypub.com/meteors. If the page does not pop up immediately, you will see a link to Sky & Telescope Magazine’s homepage, a very useful site. Or simply go to SkyandTelescope.com.
Ursa Major, The Great Bear, is the third largest constellation. But while the entire constellation may sometimes be difficult to see because of being so widely spread out, the famous asterism, The Big Dipper, is among the easiest of celestial objects to find.
A circumpolar constellation, Ursa Major is visible every night. To find it, and The Big Dipper, face north and look low to the northwest. The Big Dipper should easily stand out. By the way, the middle star in the dipper’s handle is actually the paired stars (an optical pair, in this case) Mizar and Alcor. Most binoculars will readily show that this is a double star.
My last suggested must-see sight in the summer sky is a group of three, first-magnitude or brighter stars that make up an asterism called The Summer Triangle. These stars are first, Deneb, in Cygnus and slightly west of that, Vega, in the constellation Lyra and to the south, completing the triangle, Altair, in Aquila.
Interesting, the name Summer Triangle has only recently (mid-20th century) been applied to this asterism. However, it’s not as if people hadn’t recognized it for untold years. These easily found stars have long been used as navigational aides and some people have referred to the asterism as “The Navigator’s Triangle.”
In August, sit in a comfortable chair and face south. Lean back and look directly overhead and then let your gaze wander a bit to the east. And there you will see in all its brilliance, The Summer Triangle.
Best times for viewing are around 10 pm in early August and at dusk, or just when the stars come out in late August.
This summer why not sit back and enjoy the amazing, unspoiled spectacle visible in our clear, unspoiled Maine skies? Stargazing provides a lifetime of thrills and wonder for people of every age.