From: luweitest@address.invalid   
      
   On 2015-10-10 23:20, Helpful person wrote:   
   > On Saturday, October 10, 2015 at 1:19:56 AM UTC-4, Lu Wei wrote:   
   >> I took a photo of full moon several days ago, using my iphone4s' camera,   
   >> with flash off, HDR (high dynamic range, IIRC) open. I found there is a   
   >> dark ring surrounding moon, then a bright halo (sky is clear). The halo,   
   >> I think, is by the scattering of atmosphere near the path of moon light   
   >> (Rayleigh scattering) , and for the dark ring (and there even seems a   
   >> second obscure dark ring), maybe only diffraction can explain, but how?   
   >>   
   >> This is the photo I take:   
   >> http://postimg.org/image/uptiq1trl/   
   >>   
      
   >   
   > It's not diffraction.  My guess is that's it's an artifact of image   
   processing in the camera.   
   >   
   I searched some articles, and found that I have some misunderstandings.   
   The photo I took is similar to this:   
   https://en.wikipedia.org/wiki/Corona_%28optical_phenomenon%29   
      
   So it should be a lunar corona, caused by diffraction of water droplets,   
   not Rayleigh scattering which is responsible for the whole sky. As for   
   the dark ring surrounding the moon, as you said, maybe it's an artifact,   
   caused by high dynamic range function of camera, which combines a less   
   exposure of near-moon area and a more exposure of surrounding corona,   
   thus left a dark ring at the border. Hope someone could confirm this.   
      
      
   --   
   Regards,   
   Lu Wei   
   PGP key ID: 0x92CCE1EA   
      
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