Revisiting the Northern Pinwheel Galaxy (M101)
Somehow I’ve neglected to go back to one of the showcase galaxies of the spring sky with newer equipment and software: M101, the “Pinwheel Galaxy.” Located about 21 million light-years away within Ursa Major, this relatively close galaxy shows lots of active star-forming regions revealed by red HII gas. Those red spots are nebulae in another galaxy!
With about 20 hours of total exposure time over 4 different nights, there are plenty of much, much more distant galaxies revealed in the background as well.