NGC 6633

Open Cluster NGC 6633

(= De Cheseaux No. 3

= H VIII.72

= Melotte 201 = Collinder 380)

in Ophiuchus

Right Ascension	18 : 27.7 (h:m)
Declination	+06 : 34 (deg:m)
Distance	1.04 (kly)
Visual Brightness	4.6 (mag)
Apparent Dimension	27 (arc min)

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.

NGC 6633 has been discovered by the Swiss astronomer

Philippe Loys de Cheseaux, according to the

Webb Society Deep-Sky Observer’s Handbook, Volume 3 (Open and Globular

Star Clusters), p. 3.

It was independently rediscovered by

Caroline Herschel, and been included in her

brother William’s catalog as H VIII.72.

This magnificient object is contained in a large number of observing list, e.g. as

No. “S11” in Paul Ahnert’s Easy Object List,

in the SAC 110 Best NGC List,

No. 93 in the RASC Finest NGC Objects List,

in John Caldwell’s List

and in the

Astronomical League’s Deep Sky Binocular Club List.

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Hartmut Frommert

([email protected])

Christine Kronberg

([email protected])

Last Modification: 29 Mar 1998, 12:20 MET