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Deepsky Top-100 (3): M48

M48 in Hydra is one of the "missing" Messier objects. Messier described M 48 as "Cluster of very small [faint] stars, without nebulosity; this cluster is at a short distance from the three stars that form the beginning of the Unicorn's tail" (from SEDS.ORG, Catalog of Nebulae and Star Clusters). But at the position Messier gave for this cluster, there is no star cluster to be found. In 1959 T.F. Morris identified NGC 2548 as M48, positioned 4 to 5 degrees south of Messier's catalogue entry. Since then it has been generally accepted that NGC 2548 is the object that messier described as M 48.

According to Archinal and Hynes (Star Clusters), the coordinates of M 48 are RA 08h.13m.44s, DEC -05°.45'0" (epoch 2000). M 48 is a large, bright open cluster (vm5.8) with a diameter of 30', containing about 80 stars, the brightest star shining at magnitude 8.0. It lies at a distance of 628 parsecs, or 2000 light years. M48 can be found easily. It forms an equilateral triangle with Procyon and the five star asterism that represents "the Head" of Hydra. The distance from Procyon is 14 degrees and from Hydra's head about 12 degrees.


Finder chart for M 48. Limiting magnitude 6.5. Credit and copyright SkyTools 2 by Capellasoft

Click here to download a printable finder chart (PDF)

With 7x50 binoculars, only a few stars are resolved. Most remain hidden in a fuzzy glow, that stands out very well from it surroundings. In my 8-inch telescope, at 80x to 133x this fine cluster is well resolved. About 50 stars are spread over 30' to 45'. Here is an eyepiece impression that should give you an idea of what to expect. The circle represents the cluster's border, and is about 1 degree wide.


Eyepiece impression of M48. Limiting magnitude 12.5. North is up, east is to the left.
Credit and copyright SkyTools 2 by Capellasoft

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