The August Sky

Paul Curtin

Note: August is the annual host of the Perseid meteor shower, which peaks this year on the twelfth of the month. These are popular in the north as they come late at night during our warm season. Unfortunately, this year will be marred by a waning, but still 80% illuminated, Moon. Nonetheless, if you have the opportunity to stay up late, it is a Saturday night after all, see if you can catch some of the brighter Perseids.

Some readers have mentioned that their viewing sites are less than ideal for viewing all but the brightest deep-sky objects and have requested more information on interesting stars and asterisms that can be viewed even on moonlight or hazy nights. This complaint is valid, all the more so since numerically the majority of observers (including the author!) must deal with some degree of light pollution and other adverse atmospheric conditions on a regular basis. I’ll attempt to rectify this and invite rebuke should I backslide towards too much faint-fuzzism. In return, I urge urban readers to take advantage of any opportunities to observe from dark sky locations. You may be surprised by the results of a short trip out of town.

No more dramatic demonstration of the preceding principle can be found than comparing the view of the Milky Way in town and in the country. Looking east of Lyra, we find the cross-shaped form of Cygnus embedded in spectacular star clouds. In dark skies one can trace the dark rift running south from Deneb (alpha Cygni) through the eastern side of Cygnus all the way to the galactic center in Sagittarius. The southernmost star of the cross is Albireo (beta Cygni). This is a beautiful double star system. Most observers should be able to locate the open cluster M39 northeast of Deneb. In dark skies we can find the North American Nebula east of Deneb, and the Veil Nebula south of epsilon Cygni. Observation of such emission nebulae is greatly enhanced by the use of OIII filters.

South of Cygnus is the distinctive form of Sagitta, an arrow pointed to the east. Although Sagitta is just outside the main concentration of the Milky Way, it still contains some very nice star fields. Look for the globular cluster M71 between gamma and delta Sagittae. Using binoculars, scan west from the arrow to locate the coat hanger, also known as Brocchi’s cluster.

North of Sagitta we find Vulpecula, a scattered string of stars in the Milky Way. Starting from gamma Sagittae and scanning due north we find M27, the Dumbbell Nebula. This is perhaps not as easy to locate as M57 in Lyra but is nonetheless a fantastic planetary nebula well worth the trouble of star hopping.

Following the Milky Way south we come across Aquila. Numerous stars in this constellation, including beta, delta and mu, are multiple. This is a fine region to sweep with binoculars and there a many planetary nebulae though they require dark skies and large telescopes to truly appreciate them.

Continuing southward we find the teapot asterism that constitutes the main body of Sagittarius. Use the stars of the teapot to locate a plethora of deep sky objects or simply sweep the sector for some of the most impressive star clouds to be seen from earth. One can locate M8, the Lagoon Nebula without any optical aid. It stands out in a manner similar to the Orion Nebula. To find it, start at the spout of the teapot and sweep due north. From here one can sweep in ever wider concentric counterclockwise circles to capture an amazing variety of objects.

To the south we move away from the Milky Way, and the sky becomes dark. Telescopium and Pavo contain some globular clusters, but it is the faint galaxies that really hold sway. Xi Pavonis is a lovely color-contrast double.


The Planets in August

Mercury is in the early morning twilight early in the month but disappears by the end of August.

Venus is in the morning sky, a difficult twilight object.

Mars is lost in the sun’s glare for northerners. In the south it can still be seen low in the sky after sunset.

Jupiter is in Libra. It continues to be the most observable planet this month.

Saturn slips into the morning sky this month.

Neptune is in Capricornus. The next few months are fine opportunities for locating this faint planet.

Bibliography

Burnham, Robert Jr., Burnham's Celestial Handbook, New York: Dover, 1978.

Jones, K. G. (ed.), Webb Society Deep-Sky Observers Handbook, Volume. 3, Hillside, NJ: Enslow Publishers, 1980.

Kepple, G. R., Sanner, G. W., The Night Sky Observers Guide, Richmond, Virginia: Willman-Bell, 1999.

Tirion, W., Rappaport, B., Remaklus, W., Uranometria Deep Sky Atlas, Richmond, Virginia: Willman-Bell, 2000.

Webb, T. W., Celestial Objects for Common Telescopes, New York: Dover, 1962.