Pinwheel Galaxy M101

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M101 is a large galaxy, with a diameter of 170,000 light-years. It has around a trillion stars, twice the number in the Milky Way. The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on spiral galaxy distanced 21 million light-years (six megaparsecs) away from Earth in the constellation Ursa Major.  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 that can be detected in ultraviolet images.



After so many years of absence it took me two nights to get (most) of it running.

I was able to get all devices connected and ASCOM controllable then used SkyChart to control the scope and am evaluating Sequence Generator Pro to control the imaging process. In parallel I evaluate PixInsight as my new editing software.

All new hard and software is a big challenge to master. Difficulties are mechanical, otical, software, drivers and last not least getting a working partnership and the astronomy hobby in a tight time schedule.

The first night integrations of 4h went to the bin due to obstruction with the OAG which I didnt discover – the second night I was struggling with software issues with the OAG camera (two ASI cams on one ASCOM controlled USB port seem not to work).

Resulted in a very faint signal after pre processing and the result is not great due to short integration times of 30s and 60s unguided – 120s showed minimal elongations in stars and 300s visible ones).

I need to further work on the scope’s balance – missing a part – and decided to bin the OAG who was always giving me trouble also 10 years ago in favor of a small guiding scope and a separate guiding setup to be able to run 300s to 1200s integrations.

Very happy with the camera and my Astrodon filters – still missing my Ha which is in my other camera I lent to a friend.

The current integration was 40x60s LUM and RGB 20x60s each at 2×2 binning and then doubled with Drizzle Integration in Pixinsight. For faint objects like Galaxies the integration times are much to short but the guiding issues did not allow longer times. If I had the chance to better balance the scope I assume I could run 300s with the mounts native encoders at 1088mm focal length. As the plan is to image much fainter objects I decided in parallel to elaborate another path with a guiding scope that should get me better guiding accurracy.

Also the imaging train was a challenge and I had to recycle an old M48 adapter that was slightly bent years ago which gave me some tilt in the imaging train. Corrected the tilt with washers and ordered a tilt compensator and a variable distance compensator to reach exact backfocus. AN RC design with 8″ has significant obstruction which caused some trouble with autofocussing at first but in the image showed its strengths with a great compensated field. My fears cooling the scope I had from my old SC where wrong – all good cools out like a pro.

Happy to capture photons again … travelling to places in times of the lockdown


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