The two large open star clusters straddling the Serpens-Ophiuchus border and thus called the S-O Double Cluster. They are IC 4756 at left, a very large and scattered group, and NGC 6633 at right, a more concentrated group. Both are best seen with binoculars, and the field of the 200mm telephoto lens used here simulates a binocular field of view. This is a stack of 6 x 2-minute exposures with the 200mm lens at f/2.8 and Canon 6D MkII at ISO 800.
S-O Double Cluster consisting of: IC4756 in Serpens (at left) and NGC6633 in Ophiuchus (right), two good binocular objects. Thru Vixen 108DD astrograph at f/5 with Pentax 67 body and Fujichrome 400F slide film. 540mm focal length with about 7.5° wide field. Exposure about 20 minutes long taken in moonlight from rising waning Moon. Thus the blue sky which has been emphasized rather than neutralized. Taken July 2003 from home.
The pair of large and loose star clusters on the Serpens-Ophiuchus border known as the S-O Double Cluster. IC 4756 is at left; NGC 6633 is at right. Both are fine targets for binoculars. The 7.5 x 5° field is close to a binocular field of view. This is a stack of 10 x 6-minute exposures with the SharpStar 61mm apo refractor at f/4.5 and with the Canon R6 at ISO 800. Taken from home Oct 3, 2021. Diffraction spikes added with Astronomy Tools actions.
