A pub near me sometimes has a spot light shining into the sky, apparently in case someone doesn't know where The North Gong is

. I think what I see matches your description well enough - straight, narrow, white. They seem to have the angle pretty low so the beam looks horizontal and, with all due respect, I think judging the distance of something at night whos size you don't know is very difficult, especially if it isn't moving. They tend to move it about a bit but sometimes it sits still for a while. I suppose it depends on whether there is an operator and how energetic they are. You could just set it up and go and do other things.
This is at a pretty big city pub but you'll have decide whether this sounds plausible in Marian and whether the geometry fits.
BTW back in the 80's the Stones were doing an outdoor gig in Sydney and the light show could be seen overhead from Mt Keira at the back of Wollongong. Quite faint but still obvious against darkish skies.