M101, also known as the Pinwheel Galaxy, is a Type SAB(rs)cd spiral 21 million light-years from Earth in constellation Ursa Major and its diameter is 169,300 light-years.  For comparison, our Milky Way has a diameter of 87,00 light-years.  M101 has an apparent magnitude of 7.9 and can be spotted in 10×50 binoculars.  Pierre Méchain, an observer assistant to Charles Messier, discovered this galaxy in 1781.

Lord Rosse observed the galaxy in his 72-inch-diameter Newtonian reflector during the second half of the 19th century. He was the first to make extensive notes of the spiral structure and made several sketches.

M101 has a high population of H II regions, many of which are very large and bright. H II regions usually accompany the enormous clouds of high-density molecular hydrogen gas contracting under their own gravitational force where stars form.

The list below exhibits the number of subframes used with the exposure time for each filter. All the subframes were calibrated with Flats, Darks and Biases by PixInsight. Afterwards the subframes were combined and processed to the final image.

^* 2×2 binned

Total time for collecting data for this image is 10.5 hours.