Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Eyesight dangers using telescopes
    From: Frank Reed
    Date: 2009 Jun 26, 18:38 -0700

    Bill Morris, you wrote:
    "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."
    Really? That's amazing! I would have thought that evolution would have 
    eliminated this. That is, unaided vision should be relatively immune to 
    damage from the Sun for "normal" people. Are we talking about fair-skinned 
    northern Europeans lying on equatorial beaches? That's probably info not 
    recorded in the abstracts in the medical papers... I've seen a couple of 
    articles stating that repeated glimpses of the Sun over a course of some 
    hours are associated with damage. I could imagine all-day sunbathers falling 
    into that category. Maybe they even train themselves, unintentionally, to 
    ignore the reflex to look away...
    You wrote:
    "I had assumed that the light intensity at the retina was greater, without really thinking about it."
    And I certainly assumed as much until I saw the details worked out 
    theoretically many years ago AND conducted some experiments to make sure it 
    wasn't all "smoke and mirrors". It's certainly counter-intuitive, and there 
    are plenty of specific cases of this that still confuse me.
    Navigation List archive: www.fer3.com/arc
    To post, email NavList@fer3.com
    To unsubscribe, email NavList-unsubscribe@fer3.com

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site