A galaxy far away

For the first time in, ever, I had a properly clear night. Spoiled by neighbours garden lights, security lights, porch lights, street lights etc but hey-ho, you take what you can. I had problems aligning my scope to the NCP because a security light was directly in my field of view. then I had trouble getting the galaxy targeted properly, then when I set the tracking going it appeared to be misaligned and the stars were showing as streaks. After wasting about an hour and a half of imaging time I eventually got it sorted by about 9pm. Seven hours worth of 30 seconds exposures later and the galaxy was in the bag.
After processing I ended up with six hours of good data. Here it is tweaked and cropped substantially; the galaxy is very small on the full image.
M51, the Whirlpool Galaxy is 29 million light years away. How do we know? Well we should say about that far away because there is a fair degree of latitude in the complex calculations. Depending on which source you use it can be 23 million or 32 million  light years away. The figure I used is based on the latest work using Hubble images.
Astronomical distances are built on a distance ladder where closer objects are used to get to more distant ones. The further out you go however, the more difficult it becomes to pin things down.