Hemisphere:  Northern  ·  Constellation: Ursa Major (UMa)  ·  Contains:  24 CVn  ·  85 eta UMa  ·  Alkaid  ·  Benetnasch (ηUMa)  ·  IC4263  ·  IC4278  ·  IC902  ·  M 51  ·  M51  ·  NGC 5194  ·  NGC 5195  ·  NGC5169  ·  NGC5173  ·  NGC5195  ·  NGC5198  ·  NGC5229  ·  NGC5256  ·  The star 24CVn  ·  The star Alkaid  ·  Whirlpool Galaxy  ·  Whirlpool galaxy
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M51 and Alkaid Samyang 135mm f2.8, 


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M51 and Alkaid Samyang 135mm f2.8

Technical card

Imaging telescopes or lenses: Samyang 135mm f/2

Imaging cameras: ZWO ASI071MC PRO CMOS OSC

Mounts: Orion Azeq Atlas pro

Guiding telescopes or lenses: ASTRO TECH AT66ED Guiding

Guiding cameras: Orion Starshoot Autoguider

Software: PixInsight  ·  Stark Labs pHD guiding PHD2  ·  EQMOD, Stellarium, Stellarium Scope, PHD, Backyard EOS, Astro Tortilla Nebulosity 4

Filters: Optolong L-eXtreme 2"  ·  Zwo Filter Drawer  ·  Optolong UV-IR

Accessory: Thousand Oaks Dew Controller

Dates:Dec. 5, 2020Dec. 7, 2020

Optolong L-eXtreme 2": 3x600" (gain: 90.00) -10C
Optolong UV-IR: 60x30" (gain: 90.00) -10C

Integration: 1.0 hours

Darks: ~30

Flats: ~30

Bias: ~50

Avg. Moon age: 20.59 days

Avg. Moon phase: 65.85%

Bortle Dark-Sky Scale: 7.00

Mean SQM: 18.48

Astrometry.net job: 4085836

RA center: 13h 38' 5"

DEC center: +48° 10' 13"

Pixel scale: 3.787 arcsec/pixel

Orientation: 175.102 degrees

Field radius: 3.406 degrees

Resolution: 5428x3532

Locations: Home backyard red turning white zone Bortle 8, Gilbert, Az, United States

Data source: Backyard


I thought I would capture this early in the morning after an all night session capturing data on Sh2-240. I cropped the image to resolve the tiny Whirlpool Galaxy (M51).
I liked the perspective of the extreme distance between the two featured objects. M51 lies 28 Mly away. And Alkaid is 104 ly away.



  • Final
    M51 and Alkaid Samyang 135mm f2.8, 


  • M51 and Alkaid Samyang 135mm f2.8, 




Description: Closer crop.

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Sky plot


M51 and Alkaid Samyang 135mm f2.8,