Telescope: Meade SN10 at f/4, Orion Atlas EQ-G
Camera: Canon EOS Ra
Filter: GSO IR Blocking Filter
Guide scope: Williams Optics 50mm, ASI290MM mini, PHD
Exposure: 145x20sec, ISO 800, saved as RAW
Darks: Internal (Long Exposure Noise Reduction On)
Flats: 32×1/60sec, tee shirt flats taken at dusk
Average Light Pollution: Red zone, poor transparency, bright moonlight
Lensed Sky Quality Meter: 18.1 mag/arc-sec^2
Stacking: Mean with a 1-sigma clip.
White Balance: Nebulosity Automatic
Software: Backyard EOS, Nebulosity, Deep Sky Stacker, Photoshop
M51 is a beautiful face-on spiral galaxy in Canes Venatici, just south of Alkaid, the bright star that lies at the eastern end of the Big Dipper. The spiral arm that appears to connect M51 to the nearby companion (NGC 5195) is a bit of an illusion. The companion actually lies behind M51, and if you look closely you can see that the spiral arm is silhouetted against the background galaxy. Modern observations and computer modeling suggest that the companion has made at least two passes through the main disk of M51. During the first, it approached M51 from behind, passed through the face of the galaxy, swung around in an orbit that took it in front, and then back through the disk where it lies now behind M51. These passes set off bursts of star formation that gives the arms of M51 their beautiful blue color.
Under dark skies the spiral structure of M51 shows quite well, but from my light polluted backyard all I can see are the cores of the two galaxies. On this particular evening the conditions were so bad with poor transparency and bright moonlight I ordinarily would not have attempted to image a galaxy, but I needed to get some sleep so I picked a target that I would let me catch a nap. I was surprised at how well it turned out. It’ll be neat to see how well this works when it is actually clear!
M51 currently rises in the northeast during the late evening.
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