NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Noell Wilson
Date: 2022 Oct 28, 07:34 -0700
I’m missing a 40 mm index filter on a Cassens & Plath sextant that I purchased. I’d prefer to have a glass replacement.
An ND1000 camera filter in 40 mm popped up and is described as used for “long exposure special effects, 1/1000th of the source light intensity, and 10 F-stop effects.” I didn’t know the practical effect of that when looking at the sun so I bought one.
It’s pretty dark. The sun on a bright day is still slightly brighter than I’d prefer. See photo.
As I feared, “40 mm” on a camera filter includes the mount and the glass is slightly larger than 35 mm - too small for the shade mount. The quest continues.
Just a side note: Almost all of my sextants, especially with normal, or star telescopes, can leak light around the shades and mirrors. The C&P is no exception with a slight leakage almost all around the horizon mirror. I have a pair of $16 3M welding flash safety glasses in shade 5 that I use any time I’m using a sextant in the sunshine. A decent amount of protection against a brief accidental flash.
Regards, Noell
