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Contains:  M 101, NGC 5457
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M101 Pinwheel Galaxy in HaLRGB (White Zone), 


            Douglas J Struble
M101 Pinwheel Galaxy in HaLRGB (White Zone)

M101 Pinwheel Galaxy in HaLRGB (White Zone)

Technical card

Resolution: 1830x1464

Dates:Feb. 12, 2018April 6, 2018April 7, 2018April 8, 2018April 23, 2019May 13, 2019May 14, 2019May 23, 2019

Astrnomik CLS-CCD: 2178x60" -20C bin 1x1
Astrodon Blue Tru-Balance E-Series Gen 2: 161x60" -20C bin 1x1
Astrodon Green Tru-Balance E-Series Gen 2: 161x60" -20C
Astrodon Ha 5nm: 7x240" (gain: 139.00) -20C bin 1x1
Astrodon Red Tru-Balance E-Series Gen 2: 162x60" -20C bin 1x1
Astronomik Deep-Sky B: 169x60" -20C bin 1x1
Astronomik Deep-Sky G: 139x60" -20C bin 1x1
Astronomik Deep-Sky R: 120x60" -20C bin 1x1
Astronomik Ha 6nm 1.25'': 136x120" (gain: 200.00) -20C bin 1x1

Integration: 56.5 hours

Darks: ~50

Flats: ~50

Bias: ~250

Avg. Moon age: 18.50 days

Avg. Moon phase: 60.83%

Bortle Dark-Sky Scale: 6.10 job: 3251702

RA center: 14h 3' 7"

DEC center: +54° 23' 31"

Pixel scale: 1.086 arcsec/pixel

Orientation: 26.283 degrees

Field radius: 0.353

Locations: Backyard White Zone Observatory, Taylor, MI, Michigan, United States

Data source: Backyard


Broadband is the hardest deep space astrophotography for me here in my red zone. I piled on more integration time adding it on to last year's data, as this may be the last time I work on M101 from here.

M101 is a large face-on spiral galaxy located 22 million light-years away in the constellation of Ursa Major. At magnitude +7.9, it can be glimpsed in binoculars or small telescopes from dark sites. However, this galaxy suffers from low surface brightness and in bad seeing conditions or light polluted areas is sometimes difficult to spot even with 200mm (8-inch) scopes. M101 is best seen from the Northern Hemisphere during the months of March, April and May.

M101 is also known as the Pinwheel galaxy and was discovered by Pierre Méchain on March 27, 1781. He described it as "nebula without star, very obscure and pretty large, 6' to 7' in diameter, between the left hand of Boötes and the tail of the great Bear." He communicated this to Charles Messier, who verified its position and then included it in his catalogue as one of the final entries.

Locating the part of sky where M101 is positioned is easy, since it's close to the handle of the bowl that forms the Plough or Big Dipper asterism of Ursa Major. The Pinwheel galaxy is located at one corner of an equatorial triangle formed with second magnitude stars Mizar (ζ UMa - mag. +2.2) and Alkaid (η UMa - mag. +1.8). M101 is 5.5 degrees east of Mizar (the celebrated naked eye double star) and 5.5 degrees northeast of Alkaid.



Douglas J Struble
License: None (All rights reserved)

Sky plot

Sky plot


M101 Pinwheel Galaxy in HaLRGB (White Zone), 


            Douglas J Struble