A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Tony Oz
Date: 2018 Nov 19, 06:03 -0800
On a flee market I finally managed to find a "night" (Galilean, non-inverting, 3x50) sight tube for my SNO-T (old C&P clone). I took it apart to clean the optics.
It consists of only two lenses - the object and the ocular.
But right next to the object lens there is another sitting place (~48mm screw) as if for one more lens.
As it is this sight tube gives clear and undistorted image approximately 3 times "closer" - just as advertised.
I wonder what that extra - apparently missing - lens could be? Is it really missing or is it for some sight tube modification?
Thank you in advance.
The seller asked me if I want the "day" sight tube - which inverts the image and gives ~7x magnification.
Why one tube gives "direct" non-inverted image and the other - inverted? Is it (the image inversion) useful for something navigational?