|M10: Globular Star Cluster (Ophiuchus) RA: 16h 57.2m / DEC: -04° 06'.0|
Instrument: 10-inch Starfinder
M10 is one of my favorite globular star clusters and one of more than 20 bright globulars in Ophiuchus. M10 is conveniently situated one degree west of 4.8 magnitude 30 Ophiuchi and 3.3 degrees southeast of M12. M10 is a magnitude 6.4 object appearing 12 arc minutes across in the 10-inch Starfinder at 129X. This magnification produces a 2-mm exit pupil, which is just right for many deep-sky objects. My drawing shows a smattering of 12th through 14th magnitude stars casually tossed across the face of this bright cluster and another 16 field stars. M10 features a brighter core region, approximately 4' across, which is enveloped within a gauzy nebulosity.
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Revised: February 10, 2002 [WDF]