Globular Star Cluster M-68 ( NGC 4590 )

Description in The Deep Sky Field Guide to Uranometria 2000:

Brightest stars = magnitude 12.6;
horizontal branch stars magnitude = 15.6;
concentration: high

Quote by Charles Messier (April 9th, 1780): “'Nebula without stars in Hydra; it is very faint, very difficult to see in the telescope; near to it is a 6 mag. star.”

Pierre Mechain discovered M-68 in 1780. However it was not until 1786 that William Herschel first recognized it as a globular star cluster.

This is a very rich and concentrated cluster consisting of at least 100,000 stars. However, because of it’s small size, moderate distance, and relatively dim stars, it is bested viewed in a 10 inch or larger telescope. Kopernik’s 20 inch resolves it nicely.

Although a distance and size are given above, these figures are not as accurate as those for closer globulars. The largest (and most recent) estimate is: distance = 100,000 l.y., diameter = 100 l.y.

Note: Generally, if your telescope will show stars down to the magnitude of the horizontal branch stars, you will be able to visually resolve a globular cluster.

• M-68, NGC 4590
• Magnitude: 8.2
• Constellation: Hydra
• RA: 12h 39m 30.0s
• Dec: -26d 45' 00" Epoch 2000
• Size (mins) 12
• Classification: Globular Cluster, class X (very concentrated)
  

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George Normandin, KAS

July 5th, 1997
Revised July 18th, 2001