MORE ABOUT MY BRIS SEXTANT





This is a portrait done byMartin Mrck showing me using my sextant.



My sextant is not bigger than a nail and weighs only 3 grams about a tenth of an onze.



Mostly I use three semitransparent glasses. That gives eight images of the sun. Three bright from the dubble reflections and five more not of the same brightnes.
Sometimes I make sextants with four glasses. That gives a lot more images. Sometimes I buy beamspitters from Edmond Scientific, then just two glasses gives plenty of images becouse then there are not only dubble and quadruple reflections but many of even higher order.

There is relations betwen the images. If the angles between the outside glasses and the middle one is A and B, then the angle between the outside glasses is A+B. Those are the bright images.
The five quadruple reflections are 2A, 2B, 2C, A+C, and B+C. Those reflections are less bright. There is a general formula for any number of glasses and reflections.

Some landlubbers dont understand that the Bris sextant can be accurat without an telescop. I have made thousands of observations from small boats with good Plath sextants, usually my position lines gives an triangle about three miles across. If the weather is very calm and if am lucky I can get them to lie within one mile. In stormy weather Im satisfied if I can get my position to within ten miles.
When I was rounding the Horn in June in the middle of the winter in my 19 footer from east to west, I could not get better than thirty miles accuracy, but then the weather was rugh it was cold and if I remember right the the sun did not rise higher than 11 degres at noon. With the Cape Horn current occasionaly running up to four knots navigation was not easy. In fact it was my biggest problem.

On the outher hand standing on the beach with my Bris sextant I am often able to get a position line within a tenth of a mile, on rare occasions I have been able to repeat that three times one after the outher.

Even the best sextants dont have telescopes with higher magnification than three or four times, the reason is even on a big ship its to difficult to hold the instrumenst stedy. The Bris sextant on the outher hand is so light that you can attatch it to your glasses. Than the images becomes dead stedy. Also with both hands free you got one hand for your writing and one for yourself.

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