NavList:

Well, thanks for that tip Ken. I will certainly try it next time some
stars are out here in rainy Scotland.

By "propping up" do you mean mounting on a tripod? I would guess a
photographers tripod that allows for fine forward tilt and then lock
would be a good "prop". My A-12 sextant has the appropriate screw
thread for a camera shoe. I will give that a go.

Geoffrey Kolbe



>Geoffrey,
>
>That is an interesting analogy about the target shooter.  I have always
>believed that "seaman's" eye has been underrated.  All the technical manuals
>for the aviation sextants seem to agree that the bubble should be twice the
>size of the sun.  As was pointed out, a too big bubble is hard to find the
>center of.  A too small bubble loses mobility due to the friction of the
>bubble against the top lens of bubble chamber. But why even talk about this
>when we are on land? As has been mentioned before, if the sextant is propped
>up, and the star is successively positioned against the top and bottom of
>the bubble, and the average of the two readings is taken, you have an
>extremely accurate observation. Seaman's eye is not needed.  An example is
>using an AN 5851-1 (Navy Mk V, or A-14), repeatability of readings is about
>.3 minutes. Conversely, when held in the hands, repeatability is 2 to 4
>minutes.
>
>Ken
>
>
>
Border Barrels Ltd, Newcastleton, TD9 0SN, UK
Tel: +44 (0)13873 76253   Fax: +44 (0)13873 76214


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