Spent about two months on this object in the period of rainy days and full moon and threw away half of the collected frames. This is a good LRGB target for my scope Edge HD 11 and post-processing.

C & C are welcome!

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Messier 51 - The most famous interacting galaxy companion。

M51 lies in the constellation Canes Venatici and contains a pair of galaxies Whirlpool Galaxy (Messier 51a aka NGC5194) on the right discovered by Charles Messier in 1773, and a smaller galaxy on the left (Messier 51b, aka NCG5195) discovered by Pierre Méchain in 1781.

Whirlpool Galaxy(M51a) was the first galaxy to be classified as a spiral galaxy and astronomers studied it to understand the galaxy’s spiral arms structure and galaxy interactions. Whirlpool Galaxy lies approximately 25 million light-years from Earth and has an estimated diameter of 60,000 light-years, about 25–33% the size of the Milky Way, and about 160 billion solar masses. Whirlpool Galaxy has been called a majestic spiral galaxy or a grand-design spiral galaxy based on the Whirlpool galaxy’s beautiful face-on view and closeness to Earth.

M51b (aka NGC5195) is a dwarf galaxy that is interacting with the Its companion Whirlpool galaxy.

NGC 5195 galaxy formation is highly distorted by gravitational interaction with the Whirlpool Galaxy.

Hubble's clear view shows that NGC 5195 is passing behind the Whirlpool because the dust in this tidal bridge can be seen silhouetted against the center of NGC 5195. The small galaxy has been gliding past the Whirlpool for hundreds of millions of years.

Messier 51 is one of the best-known galaxies in the sky. The Whirlpool galaxy and its companion, NGC 5195, are easily observed by amateur astronomers, and the two galaxies may even be seen with binoculars.

Technical details:

Telescope: Celestron Edge HD11 + Reducer 0.7x

Mount: Ioptron CEM60

Imaging cameras:ZWO ASI1600MM

Software: PHD2, PixInsight, Lightroom 6.4, Sequence Generator Pro, Photoshop CS6,

Location: Palo Alto, California, USA

PhotometricColorCalibration data:

Resolution ............... 0.200 arcsec/px

Rotation ................. -67.375 deg

Observation start time ... 2021-01-16 10:03:51 UTC

Observation end time ..... 2021-03-07 13:25:21 UTC

Focal distance ........... 1961.44 mm

Pixel size ............... 1.90 um

Field of view ............ 29' 3.7" x 22' 6.1"

Image center ............. RA: 13 29 48.331 Dec: +47 11 39.05

Filters: Astrodon 1.25" LRGB Gen2 E-Series Filter Sets

Astrodon 1.25" 3nm Narrowband Ha, SII, OIII filters

Lum 150x240" 10 Hours Bin1x1

Blue 57x300" 4.75 Hours Bin1x1

Green 58x300" 4.8 Hours Bin1x1

Red 60x300" 5 Hours Bin1x1