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Thank you Frank,

A few good points to be sure. I can tell you this though: there is
absolutely no danger of any ham-handed neighbour of mine ever getting
hold of my precious sextant. I twitch uncontrollably even when an expert
handles it and feel a great sense of relief when it is finally handed
back to me.

God!  I am shuddering already.

But a follow-up question: another poster (not sure if it was you Fred)
indicated that he brings the sun down to the horizon to view it; the
implied message being that it is safer. My question is, why is it any
safer to look at the sun's image by bringing it down to horizon level
than it is by setting the sextant at 0 and looking at it directly
(notwithstanding a decreased chance of neck strain). You are still
observing a very bright object; albeit one reflected to another location
by the index mirror. Even at that, you would still be blinded if the
shades suddenly fell out of line.

Robert






>Robert E asked:
>"Why is this dangerous?  Is it because there is a possibility of the
shades
>slipping out of position?"
>
>In a way, yes.
>
>Fundamentally, it is dangerous because there is a telescope in the light
>path. This is intrinsically dangerous when you're looking at the Sun. If
you carry
>this risk alone, then there's no problem. But do you??
>
>Imagine yourself out on a street corner with your sextant on June 8th.
You
>know what you're doing; nothing could go wrong. And you say to
yourself, 'I know
>what I'm doing... nothing could go wrong..."   So you demo your sextant
to
>your neighbor who happens to have heard about the transit of Venus today
and is
>enthusiastic to see the show. And you're pleased to show the show... You
swing
>the shades one way.. you swing them back... you demo the sight... You
hand
>the sextant to your neighbor and before you've noticed he swings the
shades out
>and looks straight through at the Sun. He jumps away quickly but it's
too
>late. He's got a blindspot. He has permanent damage to his eye. And
you've got a
>legal and moral nightmare.
>
>That's a parable, of course, but the fundamental concept stands; it's
>error-correction. So what do you do? How do you avoid the potential for
a minor error
>with major consequences when you're casually using a sextant to observe
the
>Sun?
>
>Frank R
>[ ] Mystic, Connecticut
>[X] Chicago, Illinois
>
>Robert E asked:

>"Why is this dangerous?  Is it because there is a possibility of the
shades

>slipping out of position?"

>

>In a way, yes.

>

>Fundamentally, it is dangerous because there is a telescope in the light
path. This is intrinsically dangerous when you're looking at the Sun. If
you carry this risk alone, then there's no problem. But do you??

>

>Imagine yourself out on a street corner with your sextant on June 8th.
You know what you're doing; nothing could go wrong. And you say to
yourself, 'I know what I'm doing... nothing could go wrong..."   So you
demo your sextant to your neighbor who happens to have heard about the
transit of Venus today and is enthusiastic to see the show. And you're
pleased to show the show... You swing the shades one way.. you swing them
back... you demo the sight... You hand the sextant to your neighbor and
before you've noticed he swings the shades out and looks straight through
at the Sun. He jumps away quickly but it's too late. He's got a
blindspot. He has permanent damage to his eye. And you've got a legal and
moral nightmare.

>

>That's a parable, of course, but the fundamental concept stands; it's
error-correction. So what do you do? How do you avoid the potential for a
minor error with major consequences when you're casually using a sextant
to observe the Sun? 

>

>Frank R

>[ ] Mystic, Connecticut

>[X] Chicago, Illinois
>

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