Namibia is not only the least densely populated country in the world; it is also one of the driest. The clear desert air is perfect for shooting stars and star trails.
I had planned the trip to coincide with the new moon so that we would have pitch-dark nights with lots of stars. For my first exposure, I waited until the sun had set and the sky was already quite dark, so no need for any filters −the foreground was lighter than the sky. The 30-second exposure with my Nikon D3, AF-S 17-35/2.8 lens, was enough to pick up some glow on the dunes in the background. It was followed by 47 four-minute exposures ( a total of 188 minutes) @ f/4, ISO 100, using a tripod and programmable cable release. The set up was left in the desert overnight, 40 miles away from our camp.
Back home, I stacked the star trail shots on top of the base layer in Photoshop to achieve the final result.