A spectacular lunar halo, also known as 22° halo, was recently seen in the sky above ESO‘s La Silla Observatory. Otherwise known as moon ring or winter halo, this is an optical phenomenon caused by the interaction of moonlight with millions of ice crystals suspended in the atmosphere.
The halo appears large; its radius is roughly the length of an outstretched hand at arm’s length.
The halo appears large; its radius is roughly the length of an outstretched hand at arm’s length. Despite appearing beautiful sight, the phenomenon creates non-optimal conditions for astronomical observations.
As noted on ESO.org, “Clouds and the bright light of the moon affect the quality and accuracy of astronomical observations. Although, that doesn’t reduce the allure of this ethereal sight, and in fact, some stars remain visible.”