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Winter galaxies

Map 6: North Equatorial 3
Gemini to Coma Berenices
ngc_3184_noao_as
NGC 3184 is a spiral galaxy located in the constellation Ursa Major.
Dan Smith/Adam Block/NOAO/AURA/NSF

This star map covers a region visible in the eastern sky on early February evenings north of the equator. It features Cancer the Crab, the northern part of Leo the Lion, Leo Minor the Lion Cub, and the southern portion of Ursa Major the Great Bear. Apart from Cancer's two open star clusters cataloged by Charles Messier, this deep-sky region features galaxies — including some great ones.

Unfortunately, Cancer is a faint constellation. If your sky is even moderately light-polluted, finding it may be a chore. The easiest way is to draw a line from Castor and Pollux, the brightest stars of Gemini, to Regulus, the brightest star of Leo. Cancer lies at the mid-point of this line.

At Cancer's center lies the Beehive Cluster (M44). You also may hear this object referred to as the Praesepe. To the naked eye from a dark site, M44 looks like a uniform haze against a starless background. This is not an object for large telescopes. Use 7x50 or 10x50 binoculars or a telescope/eyepiece combination that gives at least a 2° field of view.

Now it's time to observe some galaxies. One thing long-time observers have learned is that, no matter how big your scope is, you'll want a bigger one when you're looking at galaxies. Galaxies aren't that bright, and their light is spread over a much larger area than, say, a planet. This doesn't mean a small scope won't show anything, just that more details emerge as you increase aperture. Also, do your best to get away from any light pollution when you observe galaxies. The cores of the brightest galaxies may still show through, but you'll lose any detail in spiral arms or other outer regions. Finally, filters — which allow only a selected portion of light through — don't help. Galaxies contain all types of objects, so the light they emit contains a broad swath of the spectrum. Using a filter to view a galaxy simply will make it appear fainter.

Find Lambda Leonis just west of the Sickle of Leo and move 1½° south to the 9th-magnitude spiral galaxy NGC 2903. A 10-inch telescope shows a halo measuring 4' by 2' surrounding the galaxy's bright nucleus.

At the southern tip of Leo Minor, find NGC 3344, a magnitude 9.9 face-on spiral galaxy. A big scope shows the spiral arms well. Through small scopes, you'll see the nucleus surrounded by a faint, mottled area.

Find Mu Ursae Majoris near the border with Leo Minor and move ¾° west to NGC 3184. This magnitude 9.8 galaxy is a spiral, but you'll need at least an 8-inch scope to prove that to yourself. In a smaller scope, you'll see a uniform 4'-wide spot, with only a slight brightening in the center.

For a real galactic treat, look 5½° east of Chi Ursae Majoris for spiral galaxy M106. This magnitude 8.3 wonder displays spiral arms with bright blue areas, which are star-forming regions, and vast dust lanes.

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