Hemisphere:  Northern  ·  Contains:  M 101  ·  NGC 5457  ·  NGC 5473  ·  NGC 5477
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M101 -  Ha+LRGB and many questions :), 


            Ivaylo Stoynov
M101 -  Ha+LRGB and many questions :)
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M101 - Ha+LRGB and many questions :)

Technical card

Imaging telescopes or lenses: William Optics Megrez 80 FD

Imaging cameras: QHYCCD QHY 22

Mounts: Takahashi EM-200

Guiding telescopes or lenses: ZWO 60/280 GuideScope

Guiding cameras: QHY5L-II Mono

Focal reducers: William Optics FF/FR 0.8x II

Software: PixInsight PixInsinght 1.8 RC7  ·  PHD guiding  ·  photoshop  ·  APT - Astro Photography Tool

Filters: Astrodon HII-3nm

Dates:March 17, 2019March 31, 2019

Astrodon B Gen II: 12x300" bin 2x2
Astrodon G Gen II: 12x300" bin 2x2
Astrodon HII-3nm: 13x900" -40C bin 1x1
Astrodon L Gen II: 16x600" -40C bin 1x1
Astrodon R Gen II: 12x300" -40C bin 2x2

Integration: 8.9 hours

Avg. Moon age: 17.90 days

Avg. Moon phase: 51.37%

Basic astrometry details

Astrometry.net job: 2787867

RA center: 14h 3' 23"

DEC center: +54° 21' 46"

Pixel scale: 2.035 arcsec/pixel

Orientation: 232.738 degrees

Field radius: 0.918 degrees

Resolution: 2559x2000

Locations: Nedelkovo, near Sofia, Bulgaria

Data source: Backyard


Usually a set of various numbers is what we find first when we search for an object, however sometimes they could be quite inquiring… M101 is relatively close spiral galaxy around 21 million ly away from Erath. Its diameter is estimated to ~170 000ly and many sources state that it is much bigger than Milky Way. This is curious because our galaxy is estimated to 150-200 000ly? M101 is considered to contain ~1 trillion stars compared to 100-400 billions in our galaxy. Comparing the estimated masses there is great difference - 100 billion solar masses for M101 against 800-1 500 billion in Milky Way!? How such difference can be explained? Reading further to see that M101 has no central back hole. How big is our supermassive black hole – “just” ~4.1 million solar masses, not enough to close the numbers… Maybe we have more dwarfs, neutron stars and small black holes? M101 has shown many x-ray sources explained as stellar-mass black holes and exploded stars (i.e. there are dwarfs and neutron stars)… Very curious! Peculiar is also the mass distribution – the central bulge takes only ~3% giving most of the calculated mass to the periphery and satellite dwarf galaxies. Having a “grand spiral design” nearby gives good opportunities to take a look which we can’t have on our galaxy. After all it could be that we just don’t know enough for Milky Way yet :) And how we could know enough when we speak about galaxies! They are universes in the Universe…

Other interesting fact about M101 is that its spiral arms host more than 3 000 active large star formation, which is in the very high range compared to similar galaxies. The Ha regions were the initial idea of this project - to take a bit unusual point of view on “regular” target (see the first image – 3h 15min in Ha). It is quite interesting and the next time will try with bigger scope. After that decided to make a full course – to gather some LRGB and see what will come out. Combining 5 channels in an image was first time job for me, but am pleased with the results especially taking into account that it is just 80mm scope :) Hope that you will like it too!



Ivaylo Stoynov
License: None (All rights reserved)


  • M101 -  Ha+LRGB and many questions :), 


            Ivaylo Stoynov
  • Final
    M101 -  Ha+LRGB and many questions :), 


            Ivaylo Stoynov

Sky plot

Sky plot


M101 -  Ha+LRGB and many questions :), 


            Ivaylo Stoynov