Messier 101 is a galaxy I’ve image before. I think this is the fourth time. Each time has been with a different combination of equipment and this time it was with the most resolving system I’ve had the privilege of using.

This image is at 0.3 arcseconds per pixel and the amount of detail it captured astounds me, especially when M101 is 21 million light years away!

M101, AKA the Pinwheel Galaxy, is about twice as large in diameter as our Milky Way and contains about a trillion stars. A survey in the 1990’s found it had more than 1,600 HII regions. Those are the reddish areas of nebulosity. Five of those areas are so prominent they have their own NGC numbers. This image doesn’t show all 1,600 but it shows a bunch of them and even shows some minimal detail in them!

This image also shows there are two faint spiral arms on the bottom right of the image. I’ve never noticed these arms before. They are much fainter than the other arms and they resisted my efforts to enhance them without hurting the rest of the image. Instead, here is a starless version of the image that has been boosted to bring out the detail in those faint arms:

You can see a full resolution version of this at astrobin and I encourage you to zoom in and pan around. The amount of detail is fun to dig into! You can also find all the technical details there: https://app.astrobin.com/u/ac4lt?i=3yneoy