This exposure was five minutes. I've worked out a table that shows for the most part, exposures should be between 1min 30secs and 60 mins, figuring for reciprocity.
My G10 (which I use for my meter) metered this scene at ISO100 at 1/100@f/8. That translates to five minutes on my pinhole, reciprocity factored in. The worst case scenario, from what I can tell, will be if the G10 says the scene is 1/15@f/8. That equals 60 mins on the pinhole.
If it's darker than that I probably won't shoot, as a 60-minute exposure is probably all my patience will be able to endure.