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    Re: Variants of the Bris
    From: Andrés Ruiz
    Date: 2009 Jun 26, 10:39 +0200
    I have built quite bris sextants, and if the axis of each glass is not in the same plane, the images are not in a straight line.
    Greg, you say: "Use two pair of dark sunglasses (one over the other) to view the bright primary sun images and a single pair of medium sunglasses for dim secondary sun images."  Consulting with my astronomy club, they say that this is not correct , be careful.
    For my Bris Sextant I use welding glass filter, for solar protection must be tone 12 or superior. The problem is that with this tone I can not see the horizon, and the Bris must be used like a tradicinal mirror sextant. Only the three bright Suns can be seen.
    Using tone 3, 4 or 5, the horizon is visible, and the 8 imagenes are visible, but this is not advisable for the eye health.
    If some one have an original Bris Sextant, i wish to hear about it, how dark is the black glass?, it came with a calibration table?, is the horizon visible? what about the eye?...
    I have attached a spreadsheet for Bris Sextant calibration.
    Information about solar filters: http://eclipse.gsfc.nasa.gov/SEhelp/safety2.html
    For example, in the web there are several pages that explain how to build a sextant or how to see an eclipse, and for the shades usually use a 35 mm photo film, this is not secure for the eye.
    Andrés Ruiz
    Navigational Algorithms


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    File: 108806.bris-sextant-calibration.zip
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