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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Bris Sextant Solar Filter
From: John A
Date: 2016 Jun 15, 20:54 -0400
From: John A
Date: 2016 Jun 15, 20:54 -0400
That’s great for taking a photo, but would you want to stare at one of those sun images for several minutes, waiting for it to touch the horizon? How about several times a day on an extended voyage? I sure wouldn’t.
NOTE TO FUTURE READERS: It’s fine to use a microscope slide or whatever if you only intend to play with your Bris once or twice — if you are careful. But if you intend to actually build and *use* a Bris-style mini-sextant, do some research beyond reading this thread, and build sufficient solar filtering into your sextant to make it sun-safe. Just my opinion, but seriously, you should listen to me.
— John
On Jun 15, 2016, at 8:23 PM, Greg Rudzinski <NoReply_Rudzinski@fer3.com> wrote:John,
See image of my homemade microscope bris showing images 5,6,7,8 through a 52mm polarizer and UV camera filter. Shows dimmer than sun reflections off the water. Hasn't been a problem for me. Just dont look directly at the Sun through it.
Greg Rudzinski
From: John Almberg
Date: 2016 Jun 15, 18:31 -0400The series of reflections produced by a Bris sextant reduce the intensity of the Sun, but not nearly enough to be safe for the eye. A sun-safe solar viewing filter must *always* be used when viewing the sun through a Bris mini-sextant directly. Alternatively, you can use a pinhole to project an image of the sun through the mini-sextant onto a viewing screen.— John
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