I love the shot. Star trails are a cool thing that most everyone can do, and the results are quite impressive when done correctly. Personally, I'm itching to try it...but like so many have said, it's hard with all the light pollution...sometimes (rarely) living near the city sucks!
Either way, I'm curious about the post processing as well...sharpening, noise reduction...etc? Was it done in camera? I only ask because like exemplaria said, I've only ever seen trail shots done that were several exposures stacked together, not one 15 minute one. Not that it doesn't work, obviously, I've just seen a lot more done the other way.
The camera shoots really well in low light without the need for much noise reduction. I can't remember if I used long exposure NR in camera on this shot but my guess would be yes?