Probably the hardest image I've made for a while, both technically and practically.
My in-laws live on the Isle Of Lewis in Scotland, and heading to the coast, from here looking north-east there is no light-pollution ahead other than the Shetland Islands or Norway.... other than a great big active lighthouse.
For this reason it was a little trial and error, and lucky timing with the lighthouse flash intervals, but ultimately 1 exposure and no moon was enough to do the trick.
ISO 10,000, f/2.8, 25 sec exposures