ASTRO:
     type=Spiral galaxy
     const=Ursa Major
     mag=6.9
     dist=12 M ly
     size=92,000 ly
IMAGE:
     location=EB Driveway
     BrtlCls=4
     exposure=CMOS OSC: 122x120s (4.1h), Gain100
EQUIPMENT:
​     optics=ES102CF APO / Hyperion 24mmEP (afocal) 1.7x, FL(eff.)=1238mm, f(eff.)/12.1
     camera=ZWO ASi2600MC-Pro
     filter=Optolong L-Pro LPS
     mount=Celestron AVX
     guiding=Orion 60x240mm, ZWO ASi224MC
SOFTWARE:
     acquisition=Stellarium, APT, PHD2,
     processing=DSS, Photoshop (RCAstro, APF-R), LrC

One of the brightest galaxies in planet Earth's sky is categorized in the same size-class as our home Milky Way galaxy.  It is the big and beautiful Messier 81.  Also known as NGC 3031, and Bode's galaxy for its 18th century discoverer,  this grand design spiral can be found toward the northern constellation of Ursa Major, the Great Bear.   More specifically, it is located appx 10° northwest of Alpha Ursae Majoris (the brightest star in Ursa Major, also named "Dubhe") along with several other galaxies in the Messier 81 Group.

Messier 81 was first discovered by German astronomer Johann Elert Bode on December 31, 1774.  Thus, it is often referred to as "Bode's Galaxy".   Bode is best known for his reformulation and popularization of the Titius–Bode law.  He determined the orbit of Uranus and suggested the planet's name.  Later in 1779, Pierre Méchain and Charles Messier confirmed Bode's object, and listed it in the Messier Catalogue of non-comet-like objects.  The galaxy's large size and relatively high brightness makes it a popular target for amateur astrophotographers.  This telescopic image reveals M81's bright nucleus, spiral arms, star forming regions, and sweeping cosmic dust lanes.  Some of the dust lanes appear somewhat "errant" due to what is thought to be the lingering result of a close encounter with nearby galaxy M82 lurking just outside this view. 

M81 has been studied extensively by professional astronomers.   It has a diameter of appx 92,000 light years, which compares to appx 185,000 ly for our home Milky Way.  Its active galactic nucleus harbors a supermassive black hole of appx 70 M x the mass of our Sun.   Scrutiny of several variable stars inside M81 has yielded a well-determined distance for an external galaxy -- 11.8 million light-years.

It is estimated M81 has appx 210 globular clusters.  This compares to the currently known 142 globulars in our home Milky Way galaxy.  To date, one supernova has been recorded in Messier 81.  The supernova named SN 1993J, was discovered on 28 March 1993 by Spanish astrophysicist and astronomer Francisco García.  At the time, it was the second brightest supernova observed in the 20th century, peaking at apparent magnitude 10.7

Messier 81 is the largest galaxy in the M81 Group, a group of 34 galaxies in the constellation Ursa Major.  At approximately 12 M ly from Earth, it makes this group and the Local Group containing our home Milky Way galaxy, relative neighbors to one another within the Virgo Supercluster of galaxies.

230222 - M81 "Bode's" galaxy