Seth, I watched the video and Dr. Chou mentions that an attenuation of 10^3 for infrared is ok, and 10^5 is acceptable for the visual wavelengths. Shade Number 12 has an attenuation of 10^5 (100,000) across all of the required wavelengths. He specifically mentions that a GLASS filter should be used and not a polycarbonate filter. #14 has an attenuation of 7.2X10^5, and so attenuated the sun by an additional factor of 7.2 over the #12 filter. The #12 does appear to be safe but gives a brighter image that may be a bit uncomfortable to look at. The body of the site also suggests that an attenuation of 10^4.5 is satisfactory. # 12 seems to pass the litmus test in all of the material. I will admit that I have not read the entire text, but I have watched the presentation in the video. Does the body of the article conflict with this? Some interesting facts he brought up: 1. Eye damage is NOT thermal, but photo-chemical. In fact, the increase in temperature of the cornea is only 2 to 3 degrees C for naked eye observations. It takes an exposure of around 40 seconds to do the damage, and it doesn't show up for 24-48 hours. Most of this damage heals itself within a few weeks. 2. Smoked glass filters are good. The problem with them is that the soot falls off and the transmission increases. 3. Once the sun is near the horizon, and it has turned red it is safe to look at without a filter. I was surprised by these three facts he presented in the video. I purchased some eclipse viewers from the planetarium yesterday and have not had a chance to use them yet. They appear to be plastic with carbon black particles embedded in it. Dr. Chou mentions this type of filter and says it is safe, but the image is not as pleasing because of the light diffusion through the carbon. It leaves a halo around the disk of the sun, and decreases the detail. I am anxious to see the results for myself. Brent ________________________________ From: Seth Jarvis <SJarvis@slco.org> To: 'Utah Astronomy' <utah-astronomy@mailman.xmission.com> Sent: Friday, May 18, 2012 2:46 PM Subject: Re: [Utah-astronomy] DeLoy Brent, #14 welders' shade is _barely_ in the safe zone, physiologically speaking. It's been carefully measured. #12 might "feel" OK to look through, but dangerous amounts of IR are getting through. Retinas don't register pain. http://www.transitofvenus.org/june2012/eye-safety/280-viewing-the-transit-ey... Seth -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Brent Watson Sent: Friday, May 18, 2012 1:42 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] DeLoy Has anyone checked the welding supply houses around town? #12 welders glass is OK, but a bit bright. Best is #14. I have a couple I plan to use this weekend. I usually keep one in my truck and one in my car. Many sunspots are naked eye visible. ________________________________ From: "jcarman6@q.com" <jcarman6@q.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Friday, May 18, 2012 1:04 PM Subject: [Utah-astronomy] DeLoy Thanks for the announcement Seth. T ried to contact her yesterday about the glasses at the planetarium, but we couldn't hook up. T old her to get over to the Planetarium asap this morning. S uspect she's missed the boat, but waiting to hear from her . She might have got there around noon. It gets INCREDIBLY frustrating to have people decide they want to participate at the last minute. I'm delighted they want to go . W asn't planning on taking the C-8 with the mylar filter, but will now. I have a 3" finder scope with a #14 welder's glass ready to go. That was all I was going to take (well the camera and a tripod, of course). Hmm after loading all that, hope there's room for the chairs lol. _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Send messages to the list to Utah-Astronomy@mailman.xmission.com The Utah-Astronomy mailing list is not affiliated with any astronomy club. To unsubscribe go to: http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Then enter your email address in the space provided and click on "Unsubscribe or edit options". _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Send messages to the list to Utah-Astronomy@mailman.xmission.com The Utah-Astronomy mailing list is not affiliated with any astronomy club. To unsubscribe go to: http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Then enter your email address in the space provided and click on "Unsubscribe or edit options". _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Send messages to the list to Utah-Astronomy@mailman.xmission.com The Utah-Astronomy mailing list is not affiliated with any astronomy club. To unsubscribe go to: http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Then enter your email address in the space provided and click on "Unsubscribe or edit options".