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By Davide Simonetti
After a couple of days of clear nights and the forecast looking good for another it seemed like a good idea to go to a place with darker skies than London and try a more challenging target. Alas, the run of good weather came to an end and upon arrival at Kelvedon Common in Essex the sky was murky with only Ursa Major bright and easily visible...so revisiting M101 made sense. The poor conditions meant that even with 6 minute exposures the galaxy was only just visible on the subs so I was pleasantly surprised at how the resulting image came out.
004 x 180 second exposures at Unity Gain (139) cooled to -20°C
014 x 360 second exposures at Unity Gain (139) cooled to -20°C
074 x dark frames
030 x flat frames
100 x bias/offset frames
Total integration time = 1 hour and 36 minutes
Captured with APT
Guided with PHD2
Processed in Nebulosity, Fitsworks, and Photoshop
Telescope: Sky-Watcher Explorer-150PDS
Mount: Skywatcher EQ5
Guide Scope: Orion 50mm Mini
Guiding Camera: ZWO ASI120MC
Imaging Camera: ZWO ASI1600MC Pro
Baader Mark-III MPCC Coma Corrector
Light pollution filter
Here's my homage to galaxy season:
13x600s lum plus 12x900s lum, 24x180s each of R, G and B and 12x180s Ha used for chrominance only. Taken over 2 nights on 21st and 22nd March. Equipment as per sig, processed in Pixinsight
(Cross-posted to the Galaxy competition forum).
Capturing was a little fraught. On the first night things were fine, found a nice guide-star with the galaxy right in the middle of the frame and good guiding all night. However, the second night, with the galaxy in almost exactly the same position and orientation, but I just could not find a guide-star in my OAG. By the time I found one, the galaxy was way off centre, and I had to do some fancy footwork in processing to merge the two sets. Thankfully, I don't think you can see the join...
I was amazed at the number of faint fuzzies in the background, so I made this collage taken from the uncropped image. I don't think I got them all either, there are loads of very faint objects in the pic that don't quite look like star profiles:
This was my first attempt at this target. Which one do you prefer ?
The Pinwheel Galaxy (M101) is a face-on spiral galaxy 21 million light-years away from earth in the constellation Ursa Major. M101 is a large galaxy, comparable in size to the Milky Way with a diameter of 170,000 light-years. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses. M101 is noted for its high population of H II regions, the pinkish areas in this image, many of which are very large and bright. H II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force where stars form. H II regions are ionized by large numbers of extremely bright and hot young stars, those in M101 are capable of creating hot superbubbles. M101 is asymmetrical due to the tidal forces from interactions with its companion galaxies. These gravitational interactions compress interstellar hydrogen gas, which then triggers strong star formation activity in M101's spiral arms. It is in the M101 group of galaxies, distinct from our own Local Group, but also a member of the Virgo Supercluster of galaxies. The Virgo Supercluster contains at least 100 galaxy groups including our own, and is one of about 10 million superclusters in the observable universe.
Comments and cc welcome, hope you enjoy !
Beautiful clear night in Denmark on Sunday night, so got out there in the cold for a few hours:
(Skywatcher 200p, EQ5 goto mount unguided, Canon 450D, [42 x 120s subs @ iso 800, 16 x darks, 16 x flats, 16 x flat darks], DeepSkyStacker + Gimp for levels adjustment)
Polar alignment was a bit off, so some trailing. But I feel it's much better than my first attempt below (didn't do flats, so horrible vignetting, and focus was off, though alignment was better):
Left the scope running over night on his one when we had that cold snap, managed 42x10min luminance subs, added to some old 2x2 binned RGB data. This is a crop of the centre of the image to show off the galaxy detail a bit better. Pleased with this, although I might try a re-process when I’m not so tired.
Atik 383L+ mono, 190MN, LRGB Baader filters
thanks for looking.