Exploring the “Other Half” of Our National Parks: Stargazing Under Protected Dark Skies
Published in nationalparkstraveller.com
June 14th, 2008
BY OWEN HOFFMAN
The renowned amateur astronomer and telescope maker, John Lowry Dobson, 92, once said, “National Parks are special places where dark skies and curious minds collide.” Dobson and the famed Sidewalk Astronomers have spent three decades taking their home-made telescopes to the national parks to meet park visitors willing to stay out after dark to help them explore the “other half” of their parks.
The National Park Service recognizes that the night sky is a cross-cultural natural resource. It has taken its mission seriously to promote, protect, and preserve the “other half” of our national parks. The NPS has formed a special “Night Sky Team” that travels throughout the National Park System monitoring, measuring, and reporting on the encroachment of light pollution surrounding the parks, recognizing that our remote national parks harbor some of the last vestiges of true dark skies in the USA.
Stargazing from atop Glacier Point in Yosemite National Park is a popular summer activity.
Through the measurements and documentation provided by the NPS Night Sky Team, Natural Bridges National Monument in Utah was recently designated as the first International Dark Sky Park by the International Dark Sky Association due to its outstanding efforts to protect its night skies by installing night-sky-friendly lighting and establishing policies to protect darkness and interpret the night skies.
Amateur astronomers often come to the parks to share their knowledge and equipment with the public, using a small forest of telescopes for viewing of the heavens. Where I live in East Tennessee, the Smoky Mountain Astronomical Society frequently holds public star parties on the Foothills Parkway at Great Smoky Mountains National Park. Astronomers from the University of Tennessee often take their equipment for public events at the Big South Fork National River and Recreation Area.
If you visit the parks and stay out at night, you should know that special NPS night sky programs are offered during the summer by the National Park Service at Bryce Canyon National Park, Badlands National Park, Acadia National Park, Shenandoah National Park, Cedar Breaks National Monument, Great Basin National Park, Gila Cliff Dwellings National Monument, Rocky Mountain National Park, Lava Beds National Monument, Chaco Canyon National Cultural Historical Park, Joshua Tree National Park, and on occasion, at the rim of Crater Lake National Park.
You might also find a few of Dobson’s Sidewalk Astronomers volunteering their time, knowledge, and home-made telescopes to public service on top of Glacier Point in Yosemite, at the North and South Rim of the Grand Canyon during the June 21 to 28 Grand Canyon Star Party, and at Death Valley National Park between Christmas and New Years Day.
What to look for at night, during the summer months:
In the absence of local and distant sources of light pollution in locations free from overhead cloud cover, national park settings offer an amazing experience. So many stars become visible to the naked eye that it becomes difficult to locate familiar bright objects. But, during the long days of early summer, experiencing the night sky means staying up late, very late, as late as midnight and beyond. It also requires being out when there’s no moon, and being away from local sources of artificial lights.
From June 25th to July 7th, the evenings should be free of substantial moonlight, although the new crescent moon is visible in the west during the early evenings on July 4th through the 7th. Dark skies are again visible over our parks from July 23 through August 5th, from about 10:30 p.m. until midnight or later depending on when the waning moon is rising in the east or the waxing crescent moon is setting in the west.
If you find yourself, outside at night, without a guide or volunteer astronomer present, here are some tips for personal viewing. Of course, be sure to dress warmly, and a red filter on your flashlight will allow you to see your way without seriously impacting your dark-adapted vision.
Viewing with the unaided eye: If you have a view of the eastern horizon, look for three bright stars as dusk gives way to night. This would be at about 10:15 p.m. in the weeks surrounding the Summer Soltice (June 21st). These three stars make up the “Summer Triangle.” They are: Deneb in the constellation Cygnus (the Swan), Vega, in the constellation Lyra (the Harp), and Altair, in constellation Aquila (the Eagle). The times I will refer to in this article will vary slightly from park to park depending on where one is located with respect to the center and edge of a time zone.
Altair (17 light years distant) shines just above the eastern horizon, while Vega (25 light years distant), the brightest of the three stars, forms the peak of the Summer Triangle. Vega is about 40 degrees above the horizon. Deneb (3,300 light years distant) makes up the northeast corner of the triangle, and appears as the dimmer of the three stars (However, Deneb is actually 300,000 times the absolute brightness of the sun, but it’s much farther away, so it appears somewhat dimmer to our eyes). In the north, look for the seven stars forming the Big Dipper in the constellation Ursus major (the big bear).
The three stars in the handle of the Big Dipper form an arc that points to a bright orange star high in the sky, Arcturus (37 light years distant in the constellation Bootes, the Herdsman). Imagine a straight line past Arcturus and “spike to Spica” (the blue-white star, 260 light years distant, the brightest in the constellation Virgo). The two brightest stars in the outer bowl of the Big Dipper form a straight line that points directly to Polaris, the North Star. Polaris is at the tip of the handle of the Little Dipper in the constellation Ursus minor (the little bear).
By 11:30 p.m., the Milky Way will present a spectacular view to the unaided eye, rising over the southeastern horizon. The Milky Way runs from the southern horizon through the middle of the Summer Triangle, between Altair and Vega, through Deneb and beyond. Under dark, cloudless skies, the Milky Way will be brightly visible, as long as one is shielded from artifical lights.
Hunting stars with binoculars: Binoculars are excellent optical aids for hunting stars, especially when mounted on a tripod. Here are some binocular star-hunting tips: As it gets dark (after 11 p.m. on June 21st), try spotting the open cluster of stars known as the “Coathanger.” Look for the Coathanger along a straight line imagined between Altair and Vega. It’s located above Altair about one third of the way towards Vega in the dark dust lane of the Milky Way called the Great Rift.
Where the Milky Way intercepts the southern horizon, locate the celestial constellation Scorpio (The Scorpion), with its brightest star, the red giant, Antares, shining about 20 degrees above the southern horizon. Locate Scorpio’s curved tail and stinger. Search with binoculars (preferably mounted) along the curved base of Scorpio’s tail. There, a wonderful small cluster of stars can be observed, known informally as the “Jewell Box.” At this time of night, this multi-colored star cluster should twinkle beautifully, as it is low on the horizon.
Immediately to the east of Scorpio’s stinger, look for Ptolmey’s cluster (M-7) and the Butterfly cluster (M-6). Both can be observed in the same binocular field of view. Then, progressing eastward, following the wide path of the Milky Way, stop just above the dome and spout of the “teapot” of Sagittarius, and search with binoculars for the bright Lagoon nebula (M-8) and its companion, the Trifid nebula (M-20). Both will be in the same binocular field of view. They appear in binoculars as separate bright hazy objects surrounding a cluster of stars.
The very bright object immediately east of the Sagittarius teapot, above the southeastern horizon and below the Milky Way, is,the giant gaseous planet Jupiter. In mounted binoculars, look for Jupiter’s four Gallilean moons (their positions will change each hour). Jupiter will be visible in the night sky every month during the summer.
For observing objects in the Milky Way, the moon can interfere with its brightest. That said, the moon itself is a wonderful celestial orb to view. You can use mounted binoculars to look at the moon’s craters. However, the moon is best viewed using a telescope, three days either side of first or last quarter (the craters are highly accentuated with elongated shadows).
During full moon, it’s time to go for a night hike. When the moon rises, some of the detail of the night sky is obscured by the presence of moonlight. But, take time to observe craters on the moon with binoculars or telescopes. When the moon is full, simply go out and explore on foot without the aid of a flashlight as it’s so naturally bright in the absence of artificial lights your night-adapted eyes can see color and lots of detail. A flashlight is not needed. During the summer months, full moon hikes are part of the interpretive program at Bryce Canyon (June 17 and 18, July 17 and 18, August 15 and 16, and Sept. 15 and 16).
Of course, there’s much more to see when out exploring the “other half of the park” at night — the Perseid Meteor Showers in August, for one example, are incredible to view in the darkness of a national park — but the few naked-eye and binocular objects I have described should provide a reasonable introduction for night sky observing when out alone and driven by innate curiosity and the overwhelming beauty of the heavens above.
Owen Hoffman is a former National Park Ranger-Naturalist who worked at Crater Lake National Park, Zion National Park and Yosemite National Park.
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