Very well pronounced 21 degree halo over San Francisco in a sky full of wispy crap. These halos indicate a heavy load of barium particulates in the sky. Less than one gram can kill an adult human. Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on Google+ (Opens in new window) Related Leave a Reply Cancel reply Your email address will not be published. Required fields are marked *Comment Name * Email * Website Notify me of follow-up comments by email. Notify me of new posts by email.