This photo of the fourth mirror for the Giant Magellan Telescope makes the cleaning and inspection of an incredible piece of engineering looks more like some dudes cleaning out their backyard. The Giant Magellan Telescope will be an extremely large ground-based telescope situated in the Atacama Desert of Chile. It will consist of seven primary mirrors, each 8m in diameter. So far, four have already been cast at the Richard F. Caris Mirror Lab at University of Arizona — you can watch that process in action here.
In the photo above you can see the Mirror Lab crew cleaning and inspecting the fourth mirror's face plate. There's still a lot of work left, though: over the next three years, the surface will be smoothed and polished until it's the perfect shape. That's a bit less like cleaning your backyard, then.