Heading to shetland on the ferry tonight and heard a rumour there may be light activity. I’m no great snapper but have a reasonable dslr, what advice should i heed when attempting to get some shots?

Took some recently which turned put ok. 200 ASA, f5.6, 20 – 30 seconds, focus at infinity. Lights were not that strong but came out quite vividly.
A decent tripod, remote shutter release and locking up your mirror on the dslr would make the images sharper.
Good luck

Would also use the fastest wide lens you have for maximum light gathering ability.