M92 – Globular Cluster in Hercules

Telescope: Unitron 155 4” f/15 refractor, Atlas EQ-G

Camera: Canon EOS Ra full frame DSLR

Filter: 2” GSO IR Cut Filter

Guide scope: Orion 50mm Guidescope, ASI120MM, PHD, Dithered every 4 subs

Exposure: 28x120sec, ISO 800, saved as RAW

Darks: Internal (Long Exposure Noise Reduction)

Flats: 32×1/80s tee shirt flats taken at dusk

Average Light Pollution: Bortle 8, fair transparency

Lensed Sky Quality Meter: 18.5 mag/arc-sec^2

Stacking: Mean with a 1-sigma clip

White Balance: Nebulosity Automatic

Software: Backyard EOS, Deepsky Stacker, Nebulosity, Photoshop

M92 is the ‘other’ globular cluster in Hercules. M92 lies to the northeast of the popular M13 globular cluster in a relatively lonely patch of sky making it a bit harder to locate, but well worth the effort. Interestingly, M92 is listed as being fainter than M13 (Mv 6.4 for M92 vs. 5.8 for M13), but I find the core of M92 to be a tad brighter than M13. The larger apparent size of M13 likely contributes to its slightly higher total integrated brightness.

M92 currently rises in the northeast during the early evening.