Lynton Brown caught this 22-degree lunar halo this week and posted it to EarthSky Facebook. We see many, many photos of this type of halo – both around the sun and moon – which happen all over the world due to the presence of ice crystals in high cirrus clouds. Les Cowley of the website Atmospheric Optics wrote:
… 22-degree radius halos are visible all over the world and throughout the year. Look out for them (eye care!) whenever the sky is wisped or hazed with thin cirrus clouds. These clouds are cold and contain ice crystals in even the hottest climes.
The halo is large. Stretch out the fingers of your hand at arms length. The tips of the thumb and little finger then subtend roughly 20 degrees. Place your thumb over the the sun [or moon] and the halo will be near the little finger tip.
Thank you Lynton, for sharing this with us!
Eleanor Imster has helped write and edit EarthSky since 1995. She was an integral part of the award-winning EarthSky radio series almost since it began until it ended in 2013. Today, as Lead Editor at EarthSky.org, she helps present the science and nature stories and photos you enjoy. She also serves as one of the voices of EarthSky on social media platforms including Facebook, Twitter and G+. She and her husband live in Tennessee and have two grown sons.