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Contains:  M 101, NGC 5457
Getting plate-solving status, please wait...


            Gary Imm


Technical card

Resolution: 2381x2181

Dates:March 30, 2019March 31, 2019April 1, 2019April 2, 2019

Astrodon Blue 31mm Gen2 I-Series: 180x60" (gain: 139.00) -20C bin 1x1
Astrodon Green 31mm Gen2 I-Series: 180x60" (gain: 139.00) -20C bin 1x1
Astrodon Ha 31mm 5nm: 36x300" (gain: 300.00) -20C bin 1x1
Astrodon Lum 31mm Gen2 I-Series: 400x60" (gain: 139.00) -20C bin 1x1
Astrodon Red 31mm Gen2 I-Series: 180x60" (gain: 139.00) -20C bin 1x1

Integration: 18.7 hours

Avg. Moon age: 25.57 days

Avg. Moon phase: 17.50% job: 2624928

RA center: 14h 3' 8"

DEC center: +54° 22' 12"

Pixel scale: 0.783 arcsec/pixel

Orientation: 89.767 degrees

Field radius: 0.351

Locations: Backyard (Mag 20.8 - New Moon), Onalaska, Texas, United States

Data source: Backyard


This amazing object is a large face-on grand design spiral galaxy located 25 million light years away in the constellation of Ursa Major. It is 170,000 light-years across, nearly twice the diameter of our Milky Way. It is estimated to have at least one trillion stars. The asymmetry of the galaxy could be due to one of its 5 companion galaxies (all outside the image field of view) and/or a collision with another galaxy in the past.

M101 contains a number of clear examples of Vorontsov-Velyaminov rows. These are straight segments of otherwise curved galaxy arms, connected by a constant angle. Straight segments are hard to explain using gravitational theory. These rows are believed to be caused by large-scale density waves although I don't understand the exact mechanism.

These are so many things that I love about this object - the fascinating bright blue Ha region toward the bottom center of the image (NGC 5471, one of the largest known GEHRs - Giant Extragalactic H II Regions), the interplay between pink Ha regions and blue star clusters throughout the entire image, the subtle yellow glow of the galaxy core, the large number of branching galaxy arms (I count 10), and the faint distant galaxies which can be seen through the empty space between these arms.



Gary Imm
License: None (All rights reserved)

Sky plot

Sky plot




            Gary Imm