As if telescopes aren't cool enough already, two astronomers now want to fit them with sunglasses. They say polarising filters might make it possible to carry out optical astronomy when the Moon is up or even during the day. Optical telescopes sit idle for about 15 nights each month because moonlight scatters off atoms in the atmosphere and swamps the light from most stars. But Ivan Baldry and Joss Bland-Hawthorn of the Anglo-Australian Observatory at Siding Spring, Australia, realised that the scattered light has a distinct pattern of polarisation. The glare coming from the sky at 90° to the light source tends to have the same degree of polarisation.
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