NGC 1528 — ペルセウスの散開星団

NGC 1528 is a bright, moderately rich open cluster in Perseus, about 2,500 light-years away. At magnitude 6.4 it sits just on the threshold of naked-eye visibility from a dark site, and in binoculars it displays perhaps 40 to 60 stars scattered across 24 arcminutes — roughly the width of the full Moon. The cluster lies in a rich Milky Way field between the famous Perseus OB2 association and the Double Cluster, and it pairs naturally with its fainter neighbor NGC 1545, which lies less than a degree to the south-southwest. Both clusters are young (~300 million years) and share the general population of hot B-type stars typical of Perseus.

A fine binocular and small-telescope target. In 10x50 binoculars it appears as a small resolved clump of perhaps a dozen bright stars set in a hazy background. A 4-inch telescope at 40-60x is ideal: the cluster fills the field with 50+ stars arranged in several loose chains and clumps with distinct darker lanes crossing it. Pair the view with NGC 1545 to the south for a nice double-cluster session separate from the more famous NGC 869/884 pair. Best observed from October through March when Perseus is high in the evening sky.

Discovered by William Herschel on December 28, 1790. Herschel described it as 'a beautiful cluster of large stars,' noting it was easily resolved. It appears in most 19th and 20th century observing guides as a secondary Perseus target eclipsed by the fame of the nearby Double Cluster. Modern studies have refined its distance and age, confirming its membership in the young population of stars filling the Perseus arm of the Milky Way.