I found this post while Googling about star trails (http://www.naturescapes.net/112006/ej1106.htm). There’s some really good information in there about set-up, gear, and location.
There is a section about your shooting location and avoiding light noise. Perhaps I should have read this part better…..
“In general I recommend 150 miles from a major metropolitan area of 1 million plus, 125 miles from cities of 100,000 to 1,000,000, 75 miles from cities in the 50,000 range, 50 miles from a 25,000 person area, and 25 miles from a smaller town. Nothing can ruin a star trail image faster than light pollution, so this also means staying well away from any roadways or any other source of light. Humanmade light is your enemy. Use your lens hood as an additional precaution.”
My plan was to shoot south into the southern Polaris and have the beach in the foreground. The shot was ruined my light noise and the lights of the coastal houses etc… Light trails need 45min+ exposure times and I was blown out with 7 minutes and that was using a 2 stop graduated ND filter!!
I gave up and sot North (above) and got an ok results over 45 minutes. I guess I’ll have to wait until I get out in the country before I try again.