NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Refraction at the horizon.
From: Ken Gebhart
Date: 2008 Mar 17, 21:04 -0500
From: Ken Gebhart
Date: 2008 Mar 17, 21:04 -0500
At the risk of bringing up "sun squash" again (new members can search the archives under this thread), I can state that data from 200 photographs taken at sunset/ sunrise shows a 5% squash at 3 deg observed elevation at SL on Std day. Sun disk images were projected on a wall and measured with a yardstick. Maximum squash ever seen was 17%. Distortion (squash) is more easily noticed with head at 90 deg to the horizon than erect. Don't ask me why. Ken Gebhart On Mar 16, 2008, at 4:32 AM, Marcel Tschudin wrote: > > George wrote: >> "I have often seen a highly distorted Sun disc, at altitudes of >> well over 3 >> degrees, that leads me to question it as a general rule." > > Frank replied: >> I'm going to doubt you on one detail here, George. Three degrees >> is six Sun >> diameters. Now think back... have you REALLY "often" seen a "highly >> distorted Sun" at six full Sun diameters away from the horizon?? >> In my >> experience, and yes, I DO look for these phenomena every chance I >> get, all >> the action occurs at much lower angular altitudes. > > I also was questioning George's observation. The only situation I > could imagine he is referring to is the situation of the sun being > partially covered by a thin cloud stripe. Different refractions at the > upper and lower edge of the cloud result sometimes in odd-shaped sun > images. > > Marcel > > --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---