NGC 6633

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NGC 6633
Observation data (J2000.0 epoch)
Right ascension 18h 27.7m
Declination 6° 34′
Distance 1.04 kly
Apparent magnitude (V) 4.6
Apparent dimensions (V) 27′
Physical characteristics
Estimated age 660 million years
Other designations NGC 6633, De Cheseaux No. 3
H VIII.72, Melotte 201, Collinder 380

NGC 6633 is an open cluster, in the constellation Ophiuchus, that was, according to the Webb Society Deep-Sky Observer's Handbook, Volume 3 (Open and Globular Star Clusters), p. 3, discovered in 1745-46 by Philippe Loys de Chéseaux. It was independently rediscovered by Caroline Herschel, and been included in her brother's catalog as H VIII.72.

This cluster is nearly as large as the full moon, and contains 30 stars which make it shine at a total magnitude of 4.6; the brightest star is of mag 7.6. Its age was estimated at 660 million years.

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Coordinates: Sky map 18h 27m 42s, +06° 34′ 00″