June 2015 Skynotes: M101 Pinwheel Galaxy

R.A. 14h03m44.63s Dec. +54º16'35.3" (2015.6) 7.9 magnitude.
M101 is a spiral galaxy approximatly the same size as the Milky Way located in Ursa Major approx. 21 million light years away. Originally discovered by Pierre Mechain 1781 and Charles Messier added it as one of his later entries in his catalogue. William Parsons (3rd Earl of Rosse) was the first to note it's spiral structure.
This Image was taken in difficult twilight skies and my first serious attempt at widefield DSLR image.
Within the image can be seen NGC 5474 a peculiar offset dwarf galaxy thought to be distorted by the gravitational interaction with M101 & another spiral galaxy NGC 5422 the fuzzy cigar shaped blob just above the title block and many more as given below.

The image has captured the colour-contrast between the Population I blue supergiants of M101's arms and the old, yellow  Pop. II stars of its nucleus, similarly the correct colour of the edge-on spiral NGC 5422 in bottom right corner, It is possible to make out 6 galaxies in the frame besides M101, all of them Herschel discoveries of the 1780s and 90s, as identified thus from SkyMap:
Herschel I 214/NGC 5474, the blue nebula at left-hand edge about 11 o'clock from M101, mag. 11.3;
H III 790/ NGC 5477, a tiny blue smudge just above 101, about half way to the edge of frame at 1 o'clock; It gives a good impression of how spectacularly deeper Herschel's reach was than Messier's that he saw this tiny mag. 14.3 object at all;
H I 231/ NGC 5473, a mag. 12.4 blob about twice as far out, at about half-past-2; this has a radial velocity (red shift) of around 2000km/sec, apparently, a figure well beyond local random velocities which puts this galaxy about 100 million L.Y. away;
H I 230/ NGC 5422, that nice edge-on spiral at bottom right, mag. 12.9;  and at top right corner.,
H I 232/ NGC 5485 at mag. 12.3, with the much fainter and smaller H II 801/ NGC 5486 just upper right of that at mag. 13.9
 - a lot going on in that pic!
 In August 2011 a supernova SN2011fe was discovered however it is not apparent in this image.
For those wishing to see M101 visually, a modern 4-inch will indeed give a very nice view of M101 to a fully-adapted eye however, a large, low-intensity object needs a dark night, visually, and very good sky-clarity. Give it a go.

Bob Sayer


Location: HCO remote outpost _ Cornwall ;80)
Latitude  50º06'19.0" N
Longitude 005º23'00 W
Altitude 68.9 feet (21m)

Image details:
Captured: 2015-06-05
The image is a compilation of 35 x 300 sec subs.
4" Apochromatic refractor @f/5.4
Imaging Camera - Canon EOS 6D unmodified
Guiding - Celestron 80mm f5 refractor Skyris132M b/w camera
Mount EQ6 controlled by EQMOD and PHD2.
Filters: STD DSLR no additional
Captured and processed in Nebulosity 4, SkyTools and Photoshop.