M 52  8.08 2006
Image Capture Details

Optics:  Televue TV 60IS
Mount: Meade LX200
Camera: Canon 350XT
Filters: NONE

Focal Ratio:  F/6

Guiding: Meade DSI

Exposure:
41 X 45 Seconds = 30
Minutes
Time: 11:17 - 11:48 PM EST
Location: Waldwick, NJ
Click image for
higher resolution
M52 is a fine open cluster located in a rich Milky Way field. It is one of the rich clusters
for which amateur Jeff Bondono has proposed the name "salt and pepper" clusters. Ake
Wallenquist (1959) found 193 probable members in a region of 9' radius, and the density
near the center is about 3 stars per cubic parsec.

The brightest main sequence star of this cluster is of mag 11.0 and spectral type B7. Two
yellow giants are brighter: The brightest is of spectral type F9 and mag 7.77, the other of
type G8 and mag 8.22. The Sky Catalogue 2000.0 gives an age of only 35 million years,
which coincides with the value given by Woldemar Götz, who mentions that this cluster
contains one peculiar Of star, i.e. an extremely hot star with peculiar spectral lines of
ionized helium and nitrogene.

The distance of this cluster is not very well known; Kenneth Glyn Jones adopts 3,000,
Mallas/Kreimer 7,000 light years, while the Sky Catalogue 2000.0 gives 5,200 (i.e., 1,600
pc) and Götz 5,050 light years. Robert Garfinkle, in his "Star Hopping", quotes about
3,000, Harvey Pennington and George Kepple and Glen Sanner's Night Sky Observer's
Guide 3,900 light years. This uncertainty is mainly due to the high interstellar absorption
its light has suffered on its way to us, which is complicated to estimate reasonably. M52 is
classified as of Trumpler type I,2,r (Sky Catalog 2000) or II,2,r (Glyn Jones, Götz).

Adopting our value of 5,000 light years, the cluster's apparent diameter of 13.0 arc
minutes corresponds to a linear extension of 19 light years. Open cluster M52 is one of
the original discoveries of Charles Messier, who cataloged it on September 7, 1774 when
the comet of that year came close to it.  Amateurs can see M52 as a nebulous patch in
good binoculars or finder scopes. In 4-inch telescopes, it appears as a fine, rich
compressed cluster of faint stars, often described as of fan or "V" shape; the bright
yellow star is to the SW edge. John Mallas noted "a needle-shaped inner region inside a
half-circle."

M52 can be found quite easily by extending the line from Alpha over Beta Cassiopeiae by
6 1/2 degrees to the NW to 5th mag 4 Cassiopeiae; M52 is roughly 1 degree south and
slightly west of this star.

1 - http://www.seds.org/messier/m/m052.html
© 2008 David A. Trapani
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