I've always wanted to get a shot of this just never knew what conditions in the sky created it. I finally saw it happen before my eyes while talking on the phone - I quickly hung up, ran to my balcony and shot a few frames.
This works as a widescreen wallpaper at 1920 x 1080 pixels and is made for iMacs, but will fit most widescreen displays. Click on the image to obtain the full resolution file. Then right click and hit "set as desktop wallpaper"... a monkey could do it.