M92 – Globular Cluster in Hercules

Telescope: ES Comet Hunter MN6 at f/4.8, Orion Atlas EQ-G

Camera: Baader modified Nikon 610

Filter: 2” Orion Imaging Skyglow Filter

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

Exposure: 36x60sec, ISO 400, saved as RAW

Darks: Internal (Long Exposure Noise Reduction On)

Flats: 32×1/50sec, tee shirt flats taken at dusk

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

Lensed Sky Quality Meter: 18.4 mag/arc-sec^2

Stacking: Mean with a 2-sigma clip.

White Balance: Nebulosity Automatic

Software: Backyard Nikon, Nebulosity, Deep Sky Stacker, 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 late in the evening and is high overhead at dawn.