September 24, 2024

M81 & 82 – Spiral Galaxies in Ursa Major

M81 & 82 – Spiral Galaxies in Ursa Major

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

Camera: Baader modified Nikon 610

Filter: High Point 2” IR Blocking Filter

Guide scope: Williams Optics 50mm, ASI290MM mini, PHD2

Exposure: 14x120sec, Gain 200, saved as RAW

Darks: Internal (Long Exposure Noise Reduction On)

Flats: 32×1/4sec, tee shirt flats taken at dusk

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

Lensed Sky Quality Meter: 18.2 mag/arc-sec^2

Stacking: Mean with a 2-sigma clip.

White Balance: Nebulosity Automatic

Software: Backyard Nikon, Nebulosity, Deep Sky Stacker, Photoshop

This is M81 (bottom) and M82 (top), two bright spiral galaxies lying about 12 million light years away in Ursa Major. At present, these two galaxies are about 150,000 light years apart, though a few hundred million years ago the two passed very close to each other. The dark dust lane slashing across M82 is one result of this close encounter with M81 as are the blue star formation regions in M81. To the lower left is NGC 3077, another spiral galaxy. Visually, M81 shows its pearly core while M82 clearly shows prominent dark lanes cutting across its silhouette.

M81 and M82 are circum polar objects and therefore never set from mid-northern latitudes. This time of year they are fairly well placed in the northeast during the late evening and are high overhead after midnight.