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 30, 00:06 -0700
From: Bill Morris
Date: 2009 Jun 30, 00:06 -0700
Frank, you wrote: "(a model which would fit this, though not necessarily the correct one, is simple cooling by conduction: the area receiving sunlight increases with the square of the magnification while the boundary of that area, which is the part that is exposed to cooling by conduction, increases only linearly with magnification)." Beneath the retina is the choroid. Next to the retina is a network of capillary blood vessels, especially dense in the region of the fovea, and outside that a network of large and medium sized blood vessels, so it's not just the boundary that would cool by conduction. There are plenty of pictures of retinal damage from gazing at the sun with the naked eye, but I haven't come across one yet of damage from use of a telescope. Has anyone else? One would expect the area of damage to be proportional to the size of the image, just as it is for naked eye damage. I don't think anyone in this thread is arguing that the total amount of energy reaching the retina isn't increased by using a telescope. My understanding now is that the energy per unit area isn't increased. Have I got it right? Bill Morris Pukenui New Zealand --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---