Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    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
    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
    >> ----------------------------------------------------------------
    >> NavList message boards and member settings: www.fer3.com/NavList
    >> Members may optionally receive posts by email.
    >> To cancel email delivery, send a message to NoMail[at]fer3.com
    >> ----------------------------------------------------------------

    >> >> >> >> >> 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 >> >> >> > > > >

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site