Combination of 5, 120 second images. Modified Canon Digital Rebel DSLR camera.
5" f/5 refractor at prime focus.
NGC 6633 is a fairly large and scattered open cluster in Ophiuchus. The brighter stars are mostly A-type main sequence stars. Although the cluster has a magnitude of about 4.6 and many of the individual stars are relatively bright, it can be difficult to recognise the cluster because the stars are scattered over an area about the size of the full moon.