Patrick, The vertical stripes look like difraction spikes caused by the passage of the propellor in front of the light source. I don't understand this phenomenon, but others of our members certainly must. I only became aware of it recently when I was googling "hartzman masks" (mentioned on this site recently), which led me to "Bahtinov mask" and then to "diffraction spike," etc. Responding to Patrick: And while I've got your attention, anyone able to explain the vertical stripes in this image which my copilot got with her cell phone's camera? I'm guessing the stripes are somehow being caused by the propeller but I can't figure how: http://users.wirelessbeehive.com/~paw/temp/2010AUG24/2010AUG24-07.JPG Carpe Noctem, patrick Raeburn G. Kennard Kirton & McConkie 60 East South Temple, Suite 1800 Salt Lake City, UT 84111 (801) 321-4867 direct telephone (801) 328-3600 main switchboard (801) 550-6143 cell (801) 212-2075 fax rkennard@kmclaw.com