M52 - Open Cluster

M52 lies about ½° south of 4 Cassiopeiae, a reddish 5th- magnitude star about 6 degrees northwest of Beta Cassiopeiae. M52 is a very rich telescopic cluster. About 20 million years old, it measures 24 light years in diameter and contains nearly 200 members brighter than 15th magnitude. The cluster's computed central star density is 56 stars per cubic parsec; in Messier's catalogue, only M11 and M67 are denser open clusters. You will be immediately struck by the forceful presence of an 8th magnitude topaz field star on the cluster's southwestern edge. This star but leaps out at you, as if trying to steal the show. It is an imposter however, not an actual member of the cluster. Interestingly, when I first looked at the star, and then at the cluster, which has an overall bluish hue the topaz color of the star seemed even more pronounced. Webb and Smyth saw this star as orange, and Mallas recorded it as a conspicuous reddish star. Webb almost sounds sarcastic in his description of M52 "Irregular, with orange star, as is frequently the case," but he is merely noting that usually the most outstanding member of an open cluster shines with a ruddy hue. With a quick glance at low power, M52 looks like a tight ball of tiny crystal chips reflecting blue light. A longer view will reveal a little isolated patch of starlight just to the northwest of a heart-shaped central body; a much larger patch lies to the southeast. With 72 X, the shape of the cluster's stars looks rather arachnoid, like a scorpion. Thin wisps of faint stars jut from the body like tiny legs, and patches of starlight form the claws. The scorpion's swooping tail curves to the north, where it joins the topaz star. Two stinger stars follow to the east. The main, heart-shaped body of starlight contains many uniformly-bright stars caging a haze of fainter members, which requires peripheral vision to resolve. When you don't stare directly at this cage, do you see the thin, dark rift running along the southeastern side of the scorpion's body While in the vicinity, try to glimpse the elusive Bubble Nebula (NGC 7635). Only 36' southwest of M52, this very dim ring of gas, whose brightest section surrounds an 8.5- magnitude star, is only weakly visible from dark skies. Although it resembles a planetary nebula, the Bubble is a fairly ordinary HII region, a vast cloud of ionized hydrogen.

Telescope:	Takahashi TSA102 APO Refractor
Focal Length:	610 mm with a dedicated reducer/flattener
Mount:	Takahashi NJP 160
Camera	SBIG ST10XME
Guider:	SBIG ST402ME
Exposures:	9 5-Minute exposures for M52. The Bubble nebula was also imaged separately with nearly 3-hours of hydrogen alpha exposures which were used to enhance the image. The Bubble Nebula along with it's surrounding nebulosity requires a much longer exposure to be visible in the same image as the star cluster.
Location:	Cicero, IN
Software:	CCDSoft for image acquisition, processed with CCDStack and Photoshop CS2