Kemble's Cascade Cluster — きりんの散開星団

NGC 1502 is a small, bright open cluster in the northern constellation Camelopardalis, about 2,700 light-years away. It is famous less for the cluster itself than for its position at the southern end of Kemble's Cascade — a beautiful string of roughly 20 brighter stars stretching 2.5 degrees from north to south, named by amateur astronomer Father Lucian Kemble in the 1980s. The cluster contains two prominent matched white stars at its center (Struve 485, a wide visual double), with a few dozen other bright members scattered around them. It is compact, symmetric, and rich in close and optical double stars, making it a wonderful multiple-star hunting ground.

Best appreciated as the punctuation mark at the end of Kemble's Cascade. In binoculars the full cascade flows down a tilted field of view, with NGC 1502 as a tight bright knot at one end. A 4- to 6-inch telescope at 50-100x resolves the double-star heart of the cluster (Struve 485) and several other multiples. The key is to use a low-power, wide-field eyepiece first to appreciate the cascade, then zoom in on the cluster itself. Camelopardalis is a faint constellation so dark skies help enormously. Circumpolar from most of the northern hemisphere — visible year-round.

Discovered by William Herschel on November 3, 1787. The Kemble's Cascade asterism that frames the cluster was popularized by Walter Scott Houston (the 'Deep-Sky Wonders' columnist for Sky & Telescope) in a 1980 article based on a letter from Father Lucian Kemble, a Franciscan astronomer in Alberta, Canada. Kemble had noted the elegant star chain while sweeping through the region with 7x35 binoculars. The asterism and the cluster are now inseparable in modern observing lore, and the informal name 'Jolly Roger Cluster' — from the Struve 485 pair — also appears in some guides.