December 2012 Observing Targets

by Brian Cuthbertson

With winter on our doorstep, and Christmas / New Year's around the corner, observers often neglect this season's mid-evening skies. Why not save precious observing time for rising highlights like Orion? But these early winter skies also have their interesting nooks and crannies. So as time permits, poke around in a few of them and enjoy!

HU Tauri rating EASY
Eclipsing variable star in Taurus
RA 4h 38.3m Dec +20d 41.1' (2000)
Magnitude 5.9-6.7

Located in Taurus about four degrees north of Aldebaran, HU Tauri is an interesting eclipsing binary because its period of two days one hour and 21 minutes is only slightly out of step with Earth's rotation. Due to its period, every five weeks or so HU has a week-long "eclipse season" when it is dim every other evening. The star remains near minimum light for a couple of hours. A complete eclipse, from the first trace of fading to full recovery, lasts about four hours. As a bonus, HU is very easy to check due to the numerous nearby comparison stars in the Hyades around Aldebaran.

NGC 1097 rating MEDIUM
barred spiral in Fornax
RA 2h 46.3m Dec -30d 16.4' (2000)
Magnitude 9.3

NGC 1097 sits almost at the center of Fornax, the Furnace, a small rectangular constellation about 40 degrees SW of Orion, nestled in the western edge of Eridanus. This is deep sky country; bright stars are few, and galaxies are the main targets. A face-on two-armed barred spiral, NGC 1097 is fairly easy even in a 2.4-inch refractor: you'll see a 4x1.5 spot elongated SE-NW with a bright nonstellar center. A 6-inch reflector should show its elongated form and extensions, and significant detail is visible in 8-inch and 10-inch scopes.

NGC 1097 is an example of a class of galaxies with an active nucleus surrounded by a circumnuclear ring a few thousand light-years in diameter. Such rings are strong sources of hydrogen-alpha emission, indicating active formation of hot young stars. The rings apparently result when bars transport infalling material toward a galaxy's core.

IC 361 rating HARD
open cluster in Camelopardalis
RA 4h 19.0m Dec +58d 18.2' (2000)
Magnitude 11.5

IC 361 inhabits south central Camelopardalis, a faint constellation just north of Perseus, in the edge of the winter Milky Way. Expect to use a 10-inch for decent views of this cluster: it's at best an irregular, roundish and unresolved blur about 8' in diameter. A 12-inch may resolve roughly eight stars on a lumpy background. The cluster as a whole contains at least 100 stars magnitude 11 and fainter.

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