>All you need to do is erect a tent over it to cut out all ambient light

Or erect a tent as close as possible and camp out. Then you could get the lowlight at sunset and sunrise, with a bit of fancy sidelighting in the dark during the night.

And no genny needed these days, a 12V bike battery, an inverter and the right kind of bulb should do the trick. Maybe take a stepladder to get a good high vantage point, and a gardeners water sprayer to increase reflected highlights. Not forgetting the lichen polish, that's quite important as lichen can turn nasty if it's not carefuly buffed to a sparkley sheen.