The globular cluster Messier 13 (M13) in Hercules, with the small galaxy NGC 6207 above it. The very tiny galaxy IC 4617 is just visible between NGC 6207 and M13. M13 is generally considered the finest globular cluster in the northern half the sky (north of the celestial equator). This is a stack of just two images, each 6 minutes at ISO 800 with the Canon EOS Ra and Astro-Physics EDF 130mm f/6 apo refractor with the 6x7 field flattener. The images were the last two in the sequence of 10, and were the sharpest of the set. Earlier images were softer due to poorer seeing?
M13 with 130mm Astro-Physics apo at f/6 with no field flattener (slight camera tilt results in more coma at left of frame), for stack of 6 x 6 minute exposures at ISO 800 with Canon 7D (stock camera, not modified). Auto-guided with SG4. Worked perfectly. Slight rotation around guide star made it impossible for Photoshop to do an auto-align. Had to manually align.
A telephoto lens image of the globular cluster Messier 13 in Hercules. This is shot to simulate the field of view of binoculars for illustration purposes. The star at top is eta Herculis in the Keystone. The pair of red stars ar lower right at Nu1 and Nu2 Corona Borealis. This is a stack of 6 x 1-minute exposures with the 200mm lens at f/2.8 and Canon 6D MkII at ISO 800, tracked but unguided on the Mach 1 mount, on April 28, 2019.
