Aurora from Armagh


John McFarland
  Armagh Obervatory, County Armagh, Northern Ireland
Photo Title
  Aurora from Armagh
Time and Date taken
  22nd January 2005 2045UT and 2054UT
Equipment used
  Camera and Tripod
Capturing device used
  35 mm SLR camera (V2000 Vivitar) on tripod
Technical details

Fujifilm Superia 800, 15seconds and 12seconds.

Further processing by Mark Stronge - coronae photo. Applied an unsharp mask with a high clipping level to bring out stars, then a edge preserving smooth to reduce grain and enhance rings.

20050122 2045UT20050122 2054UT

Lunar Coronae -- formed when thin cloud passes in front of the Moon, or other bright objects, even other haloes. The small droplets of water in the cloud diffract and scatter the rays of light from the Moon en route to the observer's eyes, causing the formation of the coloured rings, since different wavelengths are scattered by different amounts. A white centre and blue and green ring hues are particularly noticeable in many lunar coronae. The rings can change size and radius depending on the size of the individual intervening droplets. The size of the water droplets can be determined from the radii of the rings, with the smallest droplets producing the largest coronae. There can be up to four rings formed, and they can be up to 5 or more degrees  (10 or more lunar diameters) in radius. The Moon has to be somewhat over-exposed to bring out the coronae.

Thanks for the tip-off about the aurora.



John McFarland
Armagh Observatory


  Public Web Stats
Last Updated : Tuesday, January 25, 2021

All content is Copyright © EAAS, authors and images.The East Antrim Astronomical Society is based in Ballyrobert, County Antrim, Northern Ireland.