November 21, 2024

M92 – Globular Cluster in Hercules

Telescope: Astro-Tech 8” f/8 Ritchey-Chretien, Orion Atlas EQ-G

Camera: Canon EOS Ra, Baader Mk III MPCC, GSO IR Blocking Filter

Guide scope: Astro-Tech 60mm, ZWO ASI120MM mini, PHD2

Exposure: 69x30sec, gain ISO 800 saved as RAW, dithered every 2 images

Darks: Internal

Flats: 32x1sec, Tee shirt flats taken at dusk

Average Light Pollution: Red zone, Bortle 8, fair transparency

Lensed Sky Quality Meter: 18.6

Stacking: Average, 1 sigma clip

White Balance: Nebulosity Automatic

Software: Backyard EOS, Deep Sky 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. This is likely the result the apparent size of M13 being larger than M92 giving M13 a higher total integrated brightness.

M92 currently rises in the northeast during the early evening.