Sky Object of the Month – January 2017
(Courtesy LVAS Observer’s Challenge*)
NGC 1545 – Open Cluster in Perseus (Mag. 6.2; Size 12’)
In the northeast corner of Perseus is the beautiful open cluster NGC 1528. This is not the January, 2017, Observer’s Challenge object, but it’s worth starting here before moving 1.5 degrees southeastward to our real target, the open cluster NGC 1545 Both clusters shine at magnitude 6.2, with NGC 1528 being larger and richer.
NGC 1545 lies a few arcminutes east of the 5th magnitude star b Persei, and is dominated by the wide triple star South 445 (observed and catalogued by the British astronomer Sir James South in 1825). Its three members, of magnitudes 7.1, 8.1, and 9.3, form an isosceles triangle. The brightest is a yellow-orange K5 giant. About 7.5’ north of S445 is the double star Struve 519 (magnitudes 7.9 and 9.4, separation 18.3”) whose primary is also yellow-orange.
On March 18, 1979, I observed and sketched S445 and Struve 519 using a 3-inch f/10 reflector at 60X. I failed to notice the fainter stars that comprise the bulk of NGC 1545. My Observer’s Challenge will be to re-observe the area with the 3-inch and see if I can pick out some of the dozen or so 10th to 11th magnitude members. Steven O’Meara, author of the Herschel 400 Observing Guide, reports adding 3 dozen more stars with a 4-inch scope at 101X.
Discovered by William Herschel in late December, 1790, NGC 1545 also bears the Herschel designation HVIII85 (H858) – the 85th entry in his 8th category of deep-space objects (coarsely scattered clusters of stars). It lies an estimated 2500 light years away.
Glenn Chaple for the LVAS
Finder Chart for NGC 1545 Sky Atlas 2000.0
NGC 1528 (top right) and NGC 1545 (bottom left)
NGC 1545 (S445 in center, STF 519 at top center)
Digitized Sky Survey image