NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Telescope danger to sight.
From: Robert Eno
Date: 2004 May 14, 15:37 +0100
From: Robert Eno
Date: 2004 May 14, 15:37 +0100
Ok. I'll wade into this one. To address Ted's note, I have my doubts if attempting a noon sight without shades will result in a detached retina. I am not an ophthalmologist, however, a few of my relatives had detached retinas so I made a point of reading up on the subject. Briefly, from what I have read, detached retinas are a result of the thinning of the part of the eyeball to which the retina is attached. This usually occurs in acutely near-sighted individuals because their eyeballs are more elongated or oblong in shape, thus causing physical stress on that part of the eyeball. I guess it would be akin to putting a piece of scotch tape on a partially filled balloon, then blowing the ballon up to its fullest extent. In the case of my relatives, the operation to reverse this involved, interestingly enough, "welding" the retina back in place with lasers. That's my simplified, and possibly incorrect interpretation of the materal that I have read with respect to detatched retinas. No doubt there is an ophthalmologist in the crowd who can provide a better explanation. Now that a few of you have come out of the closet, I might as well admit here that I too, have, on a few occasions, inadvertently looked directly into the sun with my sextant and with a 6X scope. It is a rather careless thing to do so I was loath to broadcast it. But there you have it. In any event, I have suffered no ill effects and a recent eye examination confirmed that my eyes are in perfect condition (except now I need reading glasses - growing old sucks). I tend to agree with previous posters that humans are attuned to shying away from looking directly at the sun and if we do by accident, it is probably for only a millisecond before our protective instincts kick in. (Ok, while we're at it, I've also caught site of a welder's flash too; despite being told a billion times to look away. Might as well tell me not to push that button). My two bits' worth. >In one of Tristan Jones' sagas I seem to recall he suffered a detached >retina following an attempt at taking a noon sight without shades. Somewhere >off the Amazon delta although he thought he was somewhere else at the time? >Ted Gerrard >tedgerrard@onetel.com ------------------- Email sent using AnyEmail (http://netbula.com/anyemail/) Netbula LLC is not responsible for the content of this email