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12th of May 2022
A Lunar Halo at the ATCA
(by Ángel R. López Sánchez)
Ángel R. López Sánchez was observing at the Australia Telescope Compact Array in 2008. He describes how this photo came about: "After a long day I walked from the control building to the lodge and saw a beautiful moon halo. I ran to my room and grabbed my camera (CANON EOS 400D, the digital camera I got as a gift from my IAC colleagues when completed my PhD) and tripod and looked for a nice position with one of the ATCA antennae (CA03 in this case). The halo didn't fit within a single exposure, so I took several images and merged them in a single final exposure." Lunar halos are have a radius of approximately 22 degrees halos (which is why they don't fit in a single exposure!). They are created when the moonlight is refracted by ice crystals in thin cirrus clouds. Similar "22-degree halos" can be seen around the sun when conditions are right.

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