The Pinwheel Galaxy (also known as M101 or NGC 5457) is a face-on spiral galaxy distanced 21 million light-years away in the constellation Ursa Major, first discovered by Pierre Méchain on March 27, 1781, and communicated to Charles Messier who verified its position for inclusion in the Messier Catalogue as one of its final entries.

Méchain described it as a "nebula without star, very obscure and pretty large, 6' to 7' in diameter, between the left hand of Bootes and the tail of the great Bear. It is difficult to distinguish when one lits the [grating] wires." William Herschel noted in 1784 that "[M101] in my 7, 10, and 20-feet [focal length] reflectors shewed a mottled kind of nebulosity, which I shall call resolvable; so that I expect my present telescope will, perhaps, render the stars visible of which I suppose them to be composed."

Lord Rosse observed M101 in his 72-inch diameter Newtonian reflector during the second half of the 19th century. He was the first to make extensive note of the spiral structure and made several sketches.

M101 is a large galaxy comparable in size to the Milky Way, with a diameter of 170,000 light-years. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses. M101 is noted for its high population of H II regions, many of which are very large and bright (shown in the above image as rich red areas). H II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force where stars form. H II regions are ionized by large numbers of extremely bright and hot young stars; those in M101 are capable of creating hot superbubbles. M101 is asymmetrical due to the tidal forces from interactions with its companion galaxies. These gravitational interactions compress interstellar hydrogen gas, which then triggers strong star formation activity in M101's spiral arms that can be detected in ultraviolet images.

On August 24, 2011, a Type Ia supernova, SN 2011fe was discovered in M101. The supernova was visual magnitude 17.2 at discovery and reached magnitude 9.9 at its peak. This was the fourth supernova recorded in M101. The first, SN 1909A, was discovered by Max Wolf in January 1909 and reached magnitude 12.1. SN 1951H reached magnitude 17.5 in September 1951 and SN 1970G reached magnitude 11.5 in January 1970. On February 28, 2006, NASA and the ESA released a very detailed image of the Pinwheel Galaxy, which was the largest and most detailed image of a galaxy by Hubble Space Telescope at the time. The image was composed from 51 individual exposures, plus some extra ground-based photos. [Source: Wikipedia].

The image was captured with the venerable Meade 12"LX200 Classic and the Atik 383L+ mono CCD at F7.16. Astronomik's LRGB filters were used. All subs were taken at 1x1 bin, -10C, and 10 minutes each.

Lum : 55 subs (9.17 hr) on Apr 26th, 29th, 30th and May 1st.

Red : 17 subs (2.83 hr) on Apr 26th, 29th and 30th.

Grn : 18 subs (3.00 hr) on Apr 26th, 29th, 30th and May 1st.

Blu : 18 subs (3.00 hr) on Apr 26th, 29th, 30th and May 1st.

Ha : 34 subs (5.67 hr) on Apr 26th, 29th and 30th.

Processing was done with PixInsight, following (for the most part) kayronjm's tutorial of Feb. 24th.

L was used to develop the Luminance image. R, G and B and Ha were collected for the color mix. Ha was factored and added to R (prior to channel combination) to enhance the Ha locations in the galaxy. This process was done in accordance with Harry's tutorial on AstroShed.

North is up, and this is a very slight crop. I may have gone a bit overboard on the Ha addition to the red channel. Maybe not.