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Bill wrote:

> If I achieve tangency with the left eye and rotate the sextant
> (handle up or down) the images will separate.  If I achieve tangency
> with the right eye and rotate the sextant (handle up or down) the
> images will overlap.

I was originally going to suggest that I didn't think that the vision
problems you described would cause you not to be able to "kiss the
horizon" with a sextant sight - but after thinking about it for half a
millisecond, it dawns on me that a fairly severe astigmatism problem
(at least that's what it sounds like from your description) possibly
*could* cause you to misjudge the point of tangency w/the horizon.

Wonder if your optometrist/optician could give you a measurement of
your "astigmatism error" (or "distortion", for lack of a better word)
in degrees and you could factor that into your sights (and in your
case, a separate correction for each eye)? Just a thought...

--
GregR




--- Bill  wrote:

>
> Alex
>
> Back to Lake Michigan/Michigan City for the weekend.  Saturday had
> very
> little air and even that was dying (big dome of high pressure moving
> through) while Hammond was seeing 10-15 kt and 15-20 kt up north.
> The high
> clouds overhead came in every possible form and were spectacular,
> better
> than text-book ideal. A great day to tie a line to a seat cushion,
> stream it
> off the stern and float along behind the boat looking at the clouds.
> I wish
> I had a camera with me.  On the downside, between glare off the 1-2
> ft
> swells and almost glass-like surface, and the following cloud cover,
> the
> horizon was almost indistinguishable under the sun (approx 48d
> elevation).
> The north and east horizon were very sharp, so I did a ton of IE
> checks
> using the natural horizon and a smoke stack 5 nm away.  They did not
> agree
> with sun IE checks, but more on that in another post.
>
> I did 4 observations, although I did not expect much as it was almost
> impossible to distinguish the horizon through a scope.  I was
> pleasantly
> surprised with the average (using horizon instead of sun IC),
> although the
> SD was well below my norm so that disappointed me. And my first set
> of
> observations trending toward over shots ever!
>
>      Error
> #1   1.0'
> #2   0.7'
> #3   0.4'
> #4  -1.2'
> Hot, biting flies, and lower clouds starting to arrive blocking the
> sun 40%
> of the time, so went swimming.
>
> AVG  0.225'
> SD   0.98'
>
> I did go back to a set 2 weeks earlier, using the natural horizon IC
> instead
> of the sun-derived IC, and AVG was reduced to -0.5' off, SD still
> 0.5'.
>
> For the record, sun-derived IC (left eye, sextant vertical is 0.4'
> +/- 0.1',
> horizon IC -0.1 +/- 0.1'
>
> Needless to say, there are some target/shades/eyeball vs IE issues
> that have
> me scratching my head
>
> Bill
>
>
>
> >
>


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