Yes, the part about battery life was a bit of a guess. I suppose most of the energy on a modern SLR is taken with the autofocussing and so on, so if the batteries would fully charged before you started it would probably be OK.
Yes, if it is dark then the only lights are the stars and occassional meteor (if lucky). So you can basically leave it open from dusk until dawn - at least when it is totally dark. But Canberra despite having a few hundred thousand people back in the late 70s was OK for a few hour exposure. I think I used my dad's old 120 size film camera with B&W film (that combination would be rare now).
I wouldn't mind trying it again, but I think the 35mm SLR camera was something else I lost when I had to split from the ex fiance in Adelaide, as well as the older Fuji digital. But the trouble to try and get them back would be much more than the value of the items. At least I ended up with some furniture, clothing, the SW radios, my computer and the newer small digital (that worked better anyway).
