The region in Serpens and Ophiuchus containing the Serpens-Ophiuchus (S-O) Double Cluster, here at top left, and the large binocular cluster IC 4655 above the cyan-tinted star Cebalrai, here at right. The S-O pair is made of IC 4756 (left) and NGC 6633 (right). Included near centre is the V-shaped asterism known as Taurus Poniatowski or the “Little Bull,” a group that resembles the Hyades in Taurus. The group was named for the King of Poland, Stanislaus Poniatowski in 1777 by Marcin Poczobutt. The constellation pattern was never accepted but the asterism, now in Ophiuchus, is a fine one for binoculars. This is a stack of 3 x 3-minute exposures with the 85mm Rokinon lens at f/2.8 and Canon 6D at ISO 800, plus an additional 3 min exposure through the Kenko Softon filter to add the star glows. Taken from home July 29, 2019. All tracked on the MSM SiFo Tracker from China as part of testing. At this focal length the little MSM tracker proved problematic as many frames were trailed. It was not reliable enough in its tracking to yield pinpoint stars in most shots.
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.
