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    Re: Variants of the Bris
    From: Greg Rudzinski
    Date: 2009 Jun 26, 08:37 -0700

    Your warning is understood. The slides that I am using are not that
    reflective so that two pair of dark sunglasses will work. A more
    reflective surface would require better filtering which I do by
    combining a pair of polarizing filters together and rotating them to a
    comfortable brightness.
    On Jun 26, 1:39�am, Andres Ruiz 
    > �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.
    > --
    > Andr�s Ruiz
    > Navigational Algorithmshttp://www.geocities.com/andresruizgonzalez/
    > �Bris Sextant calibration.zip
    > 6KViewDownload
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