M 101

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Observation place
New Mexico


TelescopePlanewave 431mm – 17″, 1940mm FL, f/4,5 with focal reducer
MountPlanewave Ascension 200HR (FLI)
Imaging cameraMicroline PL6303E (FLI) - regulated at -35o Celsius
Image typeL (RGB) (Vs for synghetic green)
ExhibitionLuminance (10 x 10 'bin 1 × 1), R and B (4 x 3' bin 2 × 2 each)
PretreatmentMaxim DL
TreatmentPhotoshop and PixInsight
Specific treatmentCreate a synthetic green image

Object description

Object typeSpiral galaxy "The Windmill Galaxy"
ConstellationBig bear
Visual magnitude7,9
Distance 22,8 million light years
Diameter170000 light years
Dimension seen from Earth28 x 28 arc minutes 
M101, nicknamed the Pinwheel Galaxy, is a spiral galaxy located in the Big Dipper. It is located at a distance of about 22,8 million light-years from the earth. She is seen from the front. The diameter of this galaxy is 170000 light years. It is 70% larger than that of the Milky Way (100000 light-years) and is about ten times the mass of our galaxy.  

In a sky without light pollution, M101 can be observed with binoculars. The extent of M101 requires the use of small magnifications for its observation. You need a telescope at least 250mm in diameter to begin to distinguish the nucleus and fragments of the spiral arms. The latter offer a very beautiful spectacle in a 400 mm telescope.  

In my image, which was taken in a sky without light pollution, we can appreciate the great beauty of this galaxy which is presented in blue tones. It can be seen that the spiral arms farthest from the heart of the galaxy have very low brightness. It is not easy to make them stand out even in a long exposure time. My luminance image is about 3 times more sensitive to light than red and blue color images. It therefore contributed greatly to fetching these low tones with a total exposure time of 1,67 hours (for the luminance image only).  
Richard Beauregard
Sky Astro - CCD
My impression "We cannot be alone in this gigantic universe"