The Zodiac constellation of Capricornus, best viewed in the fall, is home to a beautiful globular cluster.
The constellation of the Sea Goat is named Capricornus, not Capricorn. Unfortunately the term has been introduced by astrology and has made the name confusing, along with Scorpius, which is not named Scorpio.
Capricornus lies between Sagittarius and Aquarius in the southern sky during fall. The stars of Capricornus appear to form a large triangle. In mythology, Capricornus is an odd combination of part goat and part fish. The tale goes that the Greek god Pan had goat-like features. He attempted to change himself into a fish but was not entirely successful.
Stars
The brightest star in Capricornus lies to the farthest northest in the constellation. Deneb Algedi, or Delta Capricorni, shines at magnitude 2.85. It lies 38 light-years away from the sun. The next brightest star is all the way across the constellation. Beta Capricorni is a double star that lies just over 20 degrees west of Deneb Algedi. The brighter member of Beta Capricorni is Dabih at magnitude 3.05. (Dabih is an Arabic name that means "butchers".) It lies 344 light-years away. Beta 2 Capricorni is magnitude 6.09 and lies 313 light-years away. The two stars are separated by just three and a half arcminutes. See if you can resolve the two in binoculars. Another double star nearby is Alpha 1 and 2 Capricorni. Alpha 2 Capricorni also goes by the name Algedi. It is magnitude 3.58 and lies above the Beta Capricorni pair by a little more than two degrees. Alpha 1 is magnitude 4.3. The two stars are six arcminutes apart. Alpha 1 lies 686 light-years away and Algedi lies 108 light-years away.
Back by our first star, Deneb Algedi, lies a star of decent brightness. At magnitude 3.69, Nashira is about two degrees from Deneb Algedi. Six and a half degrees to the southwest is one more star of moderate brightness, magnitude 3.77 Zeta Capricorni. Use this star to find our next object.
Clusters
One grand globular cluster lies within the border of Capricornus. M30, a magnitude 7.5 grouping, is just over three degrees east of Zeta Capricorni. It spans 12 arcminutes across and is a beautiful sight even in a small telescope. M30 lies a whopping 26,000 light-years away.
Planets
As with all Zodiac constellations, planets and the sun and moon will regularly pass through Capricornus. The constellation of the Sea Goat has been playing host to Neptune for quite some time and will continue to house the eighth planet from the sun until 2011, when Neptune will pass into Aquarius. Neptune (magnitude 7.8) is drifting through the stars in the northeast corner of the constellation.
