Shooting M101 – The Pinwheel Galaxy

Originally, M101 was my “backup” target. My original was M42, but a late start meant I could only grab 20 minutes on my primary by the time I was setup, polar aligned and was obtaining semi decent sub lengths. Granted, 30 seconds isn’t fab, but it’ll do. As it was, stray light into the OTA due to the angle that M42 was at in relation to a set of floodlights across the road, coupled with it passing behind Millie’s tree, meant that it was a washout data-wise anyway. Hence the secondary, M101.

After swinging the scope 180 degrees towards the constellation Ursa Major and pointing the tube roughly where I knew M101 to be, I carried out another polar alignment and started hunting for this lovely spiral galaxy 21 million light years away. Try as I might though, I couldn’t find it. I was pointing at the apex of a more or less imaginary equilateral triangle between two of the bright stars in Ursa Major, but despite several test images of 45 seconds, I just couldn’t see it on the LCD. Something was amiss…so I turned to the web to double check my positioning…yup, I was right on that imaginary apex. So why was I missing an entire galaxy?? Back to the downloaded area map of Ursa Major, compare it with what I was visually seeing in front of me…if light bulbs appearing over one’s head was actually a thing, then I’m reasonably sure that I would’ve had the lighting department at B&Q suddenly spring into existence above mine…I WAS in fact using the wrong two stars as the base of that triangle!! Doh!!! Instead of Mizar and Alkaid, I was using Mizar and Alioth.

Once THAT was settled, I got Mizar settled in the 9 x 50 finderscope, made sure that the finder and OTA were aligned on the same star (ie Mizar), and using a star map. I star hopped to where M101 should theoretically be. A 45 second test shot, hold my breath, check the resulting image in back of camera…and there she was. Faint, but distinctly there. I was understandably terribly excited. In fact I danced a little jig. I’d previously captured M101 entirely by accident during the summer at 55mm. Previously, it had been but a faint smudge a few pixels across. THIS time, it was my target.

At 500mm using a refractor on a mount and tripod not designed for what I was asking it to do with the heavier than advised equipment load, I’m really rather happy that I was managing 45 second subs. And for once I took a set of dark frames and bias frames. Not shot any flats yet, but I will do. Darks, bias (or offsets) and flats are what are called the calibration frames and help to eliminate noise in the final stacked image. I’d already seen their benefit from shooting Comet 46P a couple of nights previously and I wanted to carry on the practice.

Anyway, the first image below is my original capture of M101 at 55mm in summer 2018, with just a Nikon D5300 and 18-55mm kit lens. The second image is at 500mm taken tonight with a SkyWatcher ST102T with the same Nikon D5300. At some point, as the winter progresses and we have crisp, clear (I hope!!) nights, then I’ll obtain more data and add to this. However, this is my first capture of a “fuzzy” as we astrophotographers and astronomers call galaxies, that ISN’T the Andromeda Galaxy (M31.)

Messier 101 -1

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