The Binocular Sky


NGC 6633

Constellation: Oph
Object Type: Open Cluster
RA:  18h 27m 15s
Dec:  +6° 30' 30"
Magnitude: 4.6
Recommended minimum aperture: 50mm

Charts for 100mm Binocular (2.5° aperture circle).   Click on a chart to print it.


This marvellous cluster is often overlooked and excluded from binocular lists because it can be tricky to find. Just over 8° ESE from Rasalhague (α Oph) is the 4th magnitude 72 Oph with the slightly dimmer 71 Oph a degree to the S of it. From 71 Oph, carefully pan one and a half fields to the SE and find a yellowish star that is about half the brightness of 71 Oph. Place this star on the NW periphery of the field and the cluster should be visible towards the SE edge.

What You Should See:

The stars in this cluster are older, and therefore more yellow, than those in many open clusters. Over twenty of these are easily resolved at ×37.