M22 – Globular Cluster in Sagittarius

Telescope: Unitron 510 5” f/16 refractor, Atlas EQ-G

Camera: Canon EOS Ra full frame DSLR

Filter: 2” ZWO IR Cut Filter

Guide scope: Williams Optics 50mm Guidescope, ASI290MM, PHD

Exposure: 50x30sec, ISO 1600, saved as RAW

Darks: Internal (Long Exposure Noise Reduction)

Flats: 32×1/10s sky flats taken at dusk

Average Light Pollution: Bortle 8, poor transparency, haze, smoke

Lensed Sky Quality Meter: 18.1 mag/arc-sec^2

Stacking: Mean with a 1-sigma clip

White Balance: Nebulosity Automatic

Software: Backyard EOS, Deepsky Stacker, Nebulosity, Photoshop

M22 is a large, bright, class 7 globular cluster in Sagittarius. With an estimated distance of 10,600 light years it is one of the closer globulars in our galaxy. In many ways M22 should outshine M13, but it can get a bit lost among the stars along the Milky Way near the Sagittarius star clouds and its light is dimmed by dust along the galactic plane. Still, it is large, bright, and easily resolves into this beautiful glow of stardust even in a modest telescope. In a large telescope it blossoms into a glorious sight. This is one of the gems of the summer sky in the northern hemisphere.

This is the second of 5 test images taken with my Unitron 510. M22 is currently rising in the southeast as the sky darkens. (Photo credit; John Graham, 7/14/2023)