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SuperMoon and SuperHalo
June 2013 the Moon was full and near perigee almost at the same time, creating a new "supermoon". Supermoons are usually about 10-15% larger than regular full Moons and 20-30% brighter. That's not a powerful difference for naked eye observations but it does lead to some effects in photos. I went to photograph the supermoon to Punta Piedras a coastal area of Rio de La Plata, the widest river in the world. It was a cold night with temperatures around 3-4C and thin cirrus clouds in the sky. Soon after the Moon rose above the river a circular halo became visible.
This is the halo at twilight, about one hour after sunset. It's not common to get pictures of halos when the sky is still blue from the sunset. It was barely visible to the naked eye and very clear in the photos.
The halo is a common 22 degrees halo, it forms when the ice crystals in the atmosphere have a random orientation but in this case random is not so random as not every night produces a halo! Normally lunar halos are dim and colorless but this was really strong and the colors could be seen with the naked eye like a rainbow this is probably because the Moon was at perigee and close creating a halo as bright as it can ever be so I called it the super-halo.
There's a lot of excellentt information about halos at the website of my friend Les Cowley. One of the things I learned there is that inside the 22 degrees of the halo there's no refraction of light and that's why the sky looks darker inside the halo. That also explains why the reflection of the Moon on the water suddenly stops.
This photo shows how coolorful the halo was, red, orange and yellow were visible, if you look carefully you will also see a secondary colorful arch below the halo, that's a rare halo either an infralateral halo or part of a 46 degrees halo.
The clouds were very thin and stars could be seen behind them, the constellation of Scorpius was almost complete inside the halo. This gives a good hint about how big the halo was, images were taken with a 14mm lens on a fullframe camera.
The halo lasted almost all night long, the contrast of the sky between inside and outside the halo was striking as well as its colors. It was a curious coincidence to find this optical phenomena on the same day as the supermoon and I think a few years will pass before I can write again about such a thing as superhalo.
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