reply to post by TKDRL
Not knowing the location, I think I could be forgiven for not knowing that there was an artificially lit bridge etc "out at sea". In general though,
its usually the case that there is significantly less light pollution, when you look out to sea, compared with looking inland, if you are in a
I think the question to ask here then is - is there any reason why it could not
be light pollution?
As an astrophotographer of nearly one and a half decades now, who has photographed the stars from many locations (including overseas), I'd consider
myself to be much more aware of event the slightest hint of it than most, and there are very few places that are free of it in my experience, except
for some very remote locations.
Certainly there are no true dark-sky observing sites within 100 miles of an major population center on the West coast where you are, although if you
head inland towards the interior, and north, there are some.
See this light pollution map here
to get an idea of where the most light polluted areas
At the end of the day, we can all theorize on what may or may not be causing it, but if you want to find out with some degree of certainty what is
causing it, you'll probably have to try an experiment/do some legwork.
My suggestions would be:
1. Go out after dark and head towards where the glow seems to be strongest. Look out in particular for the kind of street (and other) lighting used in
the area. Sodium vapor lights are distinctly orange in colour, and should be easy to spot - get up to a high vantage point if you can.
2. Beg borrow or steal a DSLR + tripod and a wide angle lens if you can. A DSLR will easily pick up the faintest of light sources given a long enough
exposure (hence the need for a tripod). Even if it's not light pollution, you'd have a high quality photographic record of the phenomena. I'd be
more than happy to talk you through it should you choose to go this route.