NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Eyesight dangers using telescopes
From: Bill Morris
Date: 2009 Jun 25, 23:52 -0700
From: Bill Morris
Date: 2009 Jun 25, 23:52 -0700
Frank From a quick scan of the medical literature on solar retinopathy it seems that you can get retinal burns without using a telescope or gazing at the sun while under the influence of "substances". Several cases are reported of people simply sunbathing at low latitudes in bright sunlight. In these people the swelling and blistering of the retina was, as expected, confined to the fovea. Nearly everyone recovers normal vision, but it can take months. Experimentally, the temperature of the retina can rise by 20 celsius. I must say that when I have unexpectedly glimpsed the sun through a sextant telescope, it has seemed mighty bright and I had assumed that the light intensity at the retina was greater, without really thinking about it. Your gentle and diplomatic explanation has convinced me otherwise. I guess that having a large area of the retina brightly illuminated is reponsible for the impression. Diplomacy on this site is not always in evidence (no, not you Frank). Douglas I hope will continue to be a valued contributor. Can we perhaps all resolve to use phrases such as "Are you perhaps mistaken?" as substitutes for more direct and acerbic versions. I can well imagine many potential contributors being put off if they hit the list while an argument, rather than polite discussion, is raging. Bill Morris Pukenui New Zealand --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---