The September Sky

Paul Curtin

Last month we mentioned Cygnus (or rather, alpha cygni) in its role as the apex of the Summer Triangle. In September we return to this rich region in search of some elusive deep-sky treasures. A sweep with binoculars will uncover the splendid star clouds and dark lanes of Cygnus, but the true showpieces require careful navigation and great patience.

Due east of Deneb (alpha cygni) we find the famous North America Nebula (NGC 7000). Smaller, and harder to glimpse, is the Pelican Nebula (IC 5067, 5070). In very dark skies the former can be detected with the naked eye, although you are more likely to find it with wide-field binoculars.

Farther south, almost on a line from Deneb through epsilon cygni (the eastern star of the Northern Cross) extended roughly 5 degrees, is a complex of emission nebulae known collectively as the Veil Nebula (NGC 6992, 6995, 6974, 6979, 6960). Kepple and Sanner suggest using a nebula filter to best appreciate these unusual objects. Locating the Veil can be difficult as it lacks the obvious guide stars that frame the Orion and Lagoon nebulae. Nonetheless, take the time to search for these truly spectacular objects.

South of Cygnus we leave the Milky Way and enter a rather sparse region. Delphinus is a compact constellation that, though charming, is sometimes said to bear more resemblance to a tadpole than to our aquatic cousins. Gamma delphini, at the northeastern point of the constellation, is a nice double star. The companion is often said to be green, although many of us consider it to be blue.

Capricornus is a large area that seems barren after the dazzling abundance of Sagittarius. South of this is the indistinct form of Microscopium. Here we begin to find the galaxies of southern spring in increasing numbers. Indus boasts even more, but once one approaches the south celestial pole, the galaxies and stars give way to great stretches of darkness.

The Planets in September

Mercury is very close to the sun this month and, thus, difficult to observe.

Venus is an early evening object this month. Look for it close to Jupiter on the evening of 2 September.

Mars rises well before midnight and is a fine morning object.

Jupiter slips into the sun's glare halfway through the month.

Saturn, in Cancer, is an early morning object.

Bibliography

Archinal, B. A., Hynes, S. J., Star Clusters, Richmond, Virginia: Willman-Bell, 2003.

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

Gupta, R. (ed.), Observers Handbook 2005, Toronto: University of Toronto Press, 2004.

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.