NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Variants of the Bris
From: Greg Rudzinski
Date: 2009 Jun 26, 08:37 -0700
From: Greg Rudzinski
Date: 2009 Jun 26, 08:37 -0700
Andre, 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. Greg On Jun 26, 1:39�am, Andres Ruizwrote: > �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 --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---