This one was taken with my camera. The picture shows the Nordic Optical Telescope in front
of the green laser beam being shot out from the 4.2 meter
William Herschel Telescope in the back.
The laser beam is emitted in hundreds of short pulses every second, is reflected in the atmosphere 15 km above, and
subsequently monitored by a receiver at the telescope.
The "flickering" of the reflected laser beam then shows the turbulence of the atmosphere, which can then be corrected for in the telescope
mirror by many little deformable mirrors, leading to a much sharper image of the astronomical object, comparable to what can be achieved from Space.
This technique is called adaptive optics, and in other words it means that, as an astronomer, you get to shoot motherfuckin' lasers at the sky!.