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Canes Venatici, the Hunting Dogs, is another difficult-to-discern constellation of the northern spring sky. Lying just southeast of Ursa Major, it is home to many challenging deep sky objects for the binocular enthusiast.

M51 (NGC 5194), the Whirlpool Galaxy, is a textbook example of a spiral galaxy, as evidenced in Figure 7.4. Lord Rosse was the first to detect its pinwheel-like structure in 1845 while viewing through his mammoth 72-inch reflector from Parsonstown, Ireland. Initially, astronomers thought that such "spiral nebulae" were actually solar systems in formation. It was not until the 1920's, when Edwin Hubble conceived the true galactic organization of the universe, that they were recognized as remote galaxies.

Most binoculars readily show M51. It dwells among the 6th- and 7th-magnitude stars of a small stellar trapezoid a few degrees southwest of Alkaid (Eta Ursae Major), the end star in the handle of the Big Dipper. Look for a round 8th magnitude glow punctuated by a conspicuous stellar nucleus.

NGC 5195 is a small irregular satellite galaxy of M51. Long exposure photographs reveal that these two are physically bound to one another by a bridge of stars and nebulosity. Unfortunately, NGC 5195 glows weakly at nearly 10th magnitude and is not likely to be seen in anything less than 11x80's. It may require even larger glasses than that. Look at its subtle protrusion on the northern edge of M51- -that will be NGC 5195.

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Note: The circle marks a 7-degree field of view, typical for 7x binoculars.

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