These simulations show the relation of blue circle (from random crystals) and blue spot (from oriented crystals). Blue spot on parhelic circle occurs where blue circle crosses it. The blue circle itself has a radius of 64°, as Ágnes Kiricsi has pointed out, and it is centered around the subanthelic point. Sun elevations in the simulations are 10°, 20° and 31°. When sun is higher than 32°, blue spot is no more seen. Simulations are made with Jukka Ruoskanen’s software.
Marko also submitted a very nice account about this phenomenon in the latest issue of Ursa Minor magazine in Finland. Thanks again on behalf of the readership. 🙂
I wonder how many here have actually seen a blue spot with their eyes.
to Jari Luomanen: I suppose no e-magazine avilable ?
In the era of film cameras the broblem was that blue spot colors bleached in the film, although the colors were prominent with naked eye. The blue color was barely seen on film and green disappeared completely. Now with digital cameras and usm we should get better photos of blue spot, but… where are the good photos?
I think I have seen blue spot only two times.
I found a nice video in Youtube showing the blue spot area quite well.
Yes, blue spot area. But whether you see there blue spot is another thing. It is just way too compressed video.
To my eyes the blue spot in that video is very clear, but sadly the quality of the video is too low for any still images to be extracted from it. But the blue spot should be there if the plate halo intensity is such as in the video.