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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2023 Jun 30, 09:00 -0700
Todd Spath, nine days ago, you asked:
"I was curious whether the smoke had any influence on refraction, or if it just diffracted and diffused the light? Unfortunately, it was past sunset before I could get my gear and make it to a natural horizon."
Test it. Yes. But no, it shouldn't have any impact on the Sun's angular position. Dust and other aerosols do not refract. On the other hand, could dust drive weird temperature distributions that would impact refraction? I doubt it, but observation is the arbiter.
When the smoke first got thick in early June, before the "AQI" became the media's favorite new parameter to announce every day, I was driving along in late afternoon and noticed the deeply reddened Sun in the sky. It appeared oval to me. But oval... the wrong way... a vertical oval! It looked slightly larger in the vertical dimension compared to the horizontal dimension. I realized after a while that it was an interesting illusion. I have seen the reddened Sun both in the real world and in photos so many thousands of times that I am accustomed to connecting vertical flattening by refraction to that appearance. In the case in question, apparently my visual perception was confused by that history, and that led to an illusion of vertical stretching. It was hard to shake off. I looked with binoculars when I got home and, sure enough, nice and circular!
Frank Reed
