The Pinwheel Galaxy

The Pinwheel Galaxy is a large ‘Grand Design’ spiral galaxy located in the constellation of Ursa Major. The galaxy lies about 21 million light years distant, but is almost twice the size of our own Milky Way, having a diameter of 170,000 light years. Due to its large intrinsic size, it is one of the larger galaxies visible in the Northern Hemisphere, so makes a good target even with a modest focal length telescope. 

The galaxy was discovered in 1781 by Pierre Mechain, who reported his discovery to Charles Messier who included it in his object catalogue with the designation M101.  Subsequently it was designated as NGC5457, and several of the bright gas cloud regions in the outer arms also have their own NGC designation.

The image above is an LRGB image, taken with a cooled mono astro-camera and using different filters for the Red, Green and Blue colours, and then an L-Pro light pollution filter to gather Luminance data. The separate images have then been combined and processed using PixInsight. The final image has then been cropped by a factor of about 2.

Image Details

  • Date: 9th/13th April 2024.
  • Telescope: Altair Astro 72EDF. Focal Length: 432mm, Aperture: F6.
  • Camera: Altair Astro 183MM Cooled Mono Astro Camera at Gain 200, Offset 40, Temp -10degC.
  • Filters: Luminance: Optolong L-Pro. RGB – Optolong RGB Filters.
  • Mount: Skywatcher HEQ5.
  • Guide Scope: Altair Astro 60mm.
  • Guide Camera: QHY5LII.
  • Exposure Details: L: 173 x 80s (3hr 51min), R: 42 x 120s (1hr 24min), G: 27 x 120s (54min), B: 28 x 120s (56min).
  • Total Integration Time: 7hr 5min.

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