Three open star clusters in constellation Cassiopeia: NGC 663 has an estimated 400 stars and spans about a quarter of a degree across the sky. The star cluster is assumed to form part of the stellar association Cassiopeia OB8, that is located in the Perseus arm of the Milky Way, along with the open clusters NGC 654, NGC 659, and some supergiant stars scattered between them, all of them having similar ages and distances.

NGC 663 (centre) with NGC 654 (top left) and NGC 659 (right), 16 November 2018, Vorst, William Optics 110 mm APO FLT f/7, Canon EOS 600D, UV-IR, UHC filter, 400 ISO, 49 frames x 30 sec, 1470 sec. Image size: (1.7 x 1.2) deg, fitswork.

Open star clusters NGC 663, NGC 654 and NGC 659  Vorst (D), 16 November 2018, William Optics 110 mm APO FLT f/7, Canon EOS 600D, UV-IR, UHC filter, 400 ISO, f = 770 mm, 1470 sec, PixInsight V 1.8.8-5

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