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Ursa Astronomical Association
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Ursa Astronomical Association

Corona - 10.10.2022 at 01.40 - 10.10.2022 at 01.50 Joensuu Observation number 109929

Visibility IV / V

Antti Taskinen, Joensuun Seulaset

Most of the time, the appearance of clouds in the night sky in the middle of an observation session tends to cause mostly negative emotions. However, this time there was such a spectacular ring in the sky that it was probably the best part of the whole session. It was already interesting to watch the formation of the circle. It seemed to twist around the Moon at first, and the ringlets were sometimes completely misshapen. The colors were strong. As the cloud cover became more uniform, the rings also became more circular and the colors faded. At best there were five rings in the ring. BR processing did not reveal them more than what was distinguished from the normal image.

Additional information
  • Lightsource of the phenomenon
    • Moonlight
  • Common atmospheric phenomena
    • Corona info

      Corona (of the sun) is a colored ring or series of rings visible in the immediate vicinity of the light source. It can appear in both clouds and fog.

      Coronae are formed in very small drops of water. The size of the droplets affects the size of the corona ring. The smaller the droplets on average, the larger the circle is.

      With the water droplets being about the same size as each other, a series of strongly colored corona rings can be seen in the sky. When the droplet size is wide, only one ring with faint colors is visible.

      A corona can also be formed by small ice crystals in the upper clouds, but such coronas are very faint.

      The corona phenomena identification in Skywatch is intended for different kinds of corona rings that appear around the Sun. The coronae of the moon and planets have their own phenomena identification selections.

      Unlike halo rings, which are located apart from the Sun or the Moon, the perimeters form a uniform field of light in the immediate vicinity of the celestial body.

      Corona. Image by Ismo Luukkonen.

      Corona in the morning mist. Photo by Iida Pennanen.


      The distortion of the corona is caused by changing droplet sizes in the cloud. Imabe by Eetu Saarti. 

      A solar corona on a thick cloud. The lack of colors and suble changes in shades is hinting about wide range of droplets in different sizes. Photo by Marko Riikonen

      Feeble vaque corona. Image by Matias Takala.


      If the size of the droplets changes drasticly, the corona may appear strongly distorted. Photo by Aki Taavitsainen.

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