by Anthony Ayiomamitis
The double cluster in Perseus comprised of the two constituent open clusters NGC 869 and NGC 884 is a spectacular sight through a low-power eyepiece. These clusters had been observed in antiquity based on the references by Hipparcus (130 BC). Both NGC 869 and 884 were first discovered by Pierre Mechain in 1781. The two member clusters are quite young in age (3.2 and 5.6 million years old) and are about 7,000 light-years away. The cluster is very easy to locate since it lies within a degree of δ-Cassiopeiae (Ruchbach, mag 2.65) and is best observed during late summer and early fall when it is directly overhead around midnight.
Technical Details:
Date: Dec 07-08, 2010 (20:00 - 00:20 UT+2)
Location: Athens, Greece (38.2997° N, 23.7430° E)
Equipment: AP 160 f/7.5 StarFire EDF, AP 1200GTO GEM, SBIG ST-10XME, SBIG AO-8, SBIG CFW10, SBIG LRGB + IR-block
Integrations: LRGB @ 2x(30:30:30:30) using 3-/6-min subs, 1.16" per pixel, CCD @ -25.0° C, two-part mosaic
Further Details: http://www.perseus.gr/Astro-DSO-NGC-0869-0884.htm