Constellation of Cancer
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Cancer
Roll mouse over picture to see constellation figures and outlines
Image and text ©2008 Akira Fujii/David Malin Images.

In the picture above, north is at the top and the image covers 29.0 x 36.3 degrees.
Image centre is located at 08:42:57.1, +16:45:10 (H:M:S, D:M:S, J2000) Astrometric data from Astrometry.net.

Cancer
Best seen in the early evening in March

Cancer (the Crab) is a rather small constellation of 506 square degrees without any bright stars, however, the stick figure above strongly hints at a crab-like shape. The ecliptic runs thorough the middle of the main stars, which makes it one of the 12 zodiacal constellations. It is best seen in the early evening in March. The most obvious feature in the image above is the large open cluster Messier 44, also known as Praesepe, which appears to the unaided eye as a fuzzy patch. It is easly resolved into numerous faint stars in binoculars, hence its popular name, the Beehive cluster.

Though inconspicuous, the constellation gave its name to the Tropic of Cancer. In ancient times Cancer was where the Sun appeared at its maximum mid-day elevation at the time of the (northern) summer solstice. Because of the precession of the equinoxes the northern summer solstice now occurs when the Sun is in Taurus. However, the Tropic of Cancer is still so names, and is the line of latitude around the northern hemisphere where the Sun is directly overhead at local noon on the day of the summer solstice (see also Tropic of Capricorn). There's much more about the solstices in Wikipedia

Main named stars in Cancer: (Greek alphabet)
Acubens (α Cnc), Altarf (Tarf, β Cnc), Asellus Australis (δ Cnc), Asellus Borealis (γ Cnc).

Adjoining constellations: Canis Minor, Hydra, Gemini, Leo, Lynx

Related images (other sources)
Crab         The Crab nebula
Crab Pol   The Crab nebula polarisation structure
AAT 112   M67, NGC 2682, an open cluster

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David Malin, 2009 October 15