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    Re: Simplified Bris Sextant
    From: �rjan Sandstr�m
    Date: 2012 May 08, 18:52 +0200

    It is a bit of a wait, but method is not much different than using
    precomputed altitudes in a more extreme manner than when normally
    shooting stars.
    
    I followed Sven's advice and fastened it to my sunglasses by clip
    (slaughtered a pair of cheap clip-on shades bought at petrol station),
    it gives a very stable image and I can do other things while waiting for
    sun image to approach horizon (like sitting on the ice fishing).
    
    I have mine calibrated for the four lowest suns, this far it has been
    within 1', not as good as my metal sextant but for something that can be
    carried inside a film can with plenty of room to spare it is impressive.
    
    I hope I give the information bellow correctly, this is from memory of
    something I read once over a decade ago (1997-1998 iirc), so likely I am
    not 100% correct on procedure this person used, and definitely out on
    vocabulary.
    I have had a link to a web-page that used a laser (the kind used by
    surveyors) and a theodolite to get the correct angles in a bris, he set
    this up inside a sports arena.
    If I remember it correctly it was important to take great care that both
    theodolite and bris shared the same "axle of rotation", the bris has no
    axle of rotation, but I guess it has some kind of "focal point"?
    The method required you to use sun semi diameter, dip, refraction... to
    get the correct angles but we are used to that :-)
    
    
    2012-05-08 05:15, Alexandre E Eremenko skrev:
    >
    > Greg,
    >
    > I have to say that I do not find this Bris very practical.
    > It is rather a toy than a navigation device.
    > The reason is that you have to wait for these pre-assigned moments,
    > there are few of them during the day, and at these moments
    > Sun can be obscured by a cloud, or you can be busy with something
    > else, or just miss the moment.
    >
    > I am interested to hear from a list member who managed to
    > gratuate his/her Bris sextant:-)
    >
    > Alex.
    >
    > On Mon, 7 May 2012, Greg Rudzinski wrote:
    >
    >>
    >> Making a simplified Bris  Sextant only requires gluing two microscope
    >> slides together with a gap at one end. The larger the gap the greater
    >> the angular deflection of the reflected Sun. I used a 0.7 mm pencil
    >> lead to set a gap and got 1* 57.8' of deflection. Inspect the linked
    >> image and you will see that the reflected image is the sum of four
    >> images one on top of the other. This must be from the front and back
    >> surface reflections from each slide. The best a navigator can
    >> probably hope for is 1' to 2' of precision on a home made version.
    >> Still this is pretty good for something that can get lost in a shirt
    >> pocket.
    >>
    >> Greg Rudzinski
    >> ----------------------------------------------------------------
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    >> 
    File:


    >> >> >> >> >> Attached File: http://fer3.com/arc/img/119461.f1-img_1189.jpg >> >> >> View and reply to this message: http://fer3.com/arc/m2.aspx?i=119461 >> >> >> > > > >

       
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