THE 5-metre Hale telescope at the Palomar Observatory in California can now produce pictures of the cosmos that rival some snapped by the Hubble Space Telescope.
Like many telescopes, Hale uses adaptive optics: modifying the shape of its mirror cancels the “twinkling” of starlight caused by currents in the atmosphere, but this works only in the infrared.
Now engineers at California Institute of Technology in Pasadena, which runs Palomar, and the University of Cambridge, have made Hale do the same thing at visible wavelengths. Their trick is to use a digital detector that produces 1000 electrons for every photon…
