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» Online Classroom   » Celestial Navigation   » Public Discussion of Cel Nav   » Adequate Index shades?

Author Topic: Adequate Index shades?

 - posted April 13, 2020 07:04 PM      Profile for Lance           Edit/Delete Post 
I'm using a Davis Mk 25 plastic sextant. I'm finding on sun shots that the sun is uncomfortably bright in the reflected image, even with all the index shades in use. As I type, about 10 minutes after taking a sun sight, I'm just losing the after image in my eye from the brilliant sun. I found it even worse in the tropics on a recent cruise. Adding sunglasses helps, but only a little, and I don't know whether it introduces errors.

Does anybody else have this problem? Does the Astra Mark IIIB sextant (or any other) have stronger index shades?

From: Hobart, Australia
David Burch

 - posted April 14, 2020 07:46 AM      Profile for David Burch           Edit/Delete Post 
Metal sextants, including the Astra, do have much better shades. Rarely an issue with any of them. You can jury rig extra shades for the Mk25. You can use the method of shade making we present in How to Use Plastic Sextants, but use colored filter not the full sun filter we use there.
From: Starpath, Seattle, WA

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