The contrasting open star clusters in Puppis: NGC 2477, the rich condensed cluster at left, and NGC 2451, the loose and sparse but bright open cluster at right. It has a prominent yellow star amid the blue stars.
This is with the Borg 77mm astrographic apo refractor (330mm focal length) at f/4.3 for a stack of 5 x 8 minut exposures with the filter-modified Canon 5D Mark II at ISO 800.
The Amazing Sky 