Perseus double cluster
Two open clusters about 0.5 degrees apart in the sky between Cassiopeia and Perseus. Catalogued as NGC 869 and 884 but known from earlier times as h and χ (chi) Per. The clusters are just visible to the naked eye as a fuzzy patch and so have been known since ancient times but their nature only became clear through telescopes.
Canon EOS5DMkII 254mm Newtonian @ 1200mm 13 x 15s f/4.8 ISO6400 2010-10-18 21:58:42-22:04:02 UT
From Rookhope 54.8
NGC 869 is the upper of the two clusters in this image. Each has a diameter of about 70 light years and they lie about 7,500 light years from us. Notice that there are a number of red stars around. They are M-type supergiants.
The double cluster also appears in one of my images of the Heart Nebula (IC1805).