NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: 12-power sextant scopes... Why?
From: Al Stewart
Date: 2024 Jan 6, 11:02 -0800
From: Al Stewart
Date: 2024 Jan 6, 11:02 -0800
So, I tried out the 12x20 inverting scope with my Simex Mariner at the seaside this morning...
Saturday 06 January 2024 in Kingston, GPS position N17° 56.6' W76° 45.5', Index Error 4.3' ON the arc, Height of eye 16 ft, Times all UTC by GPS Anti-Spoof App (no error), METAR conditions Temp 30° C, Press. 1016 hPa, Visibility 10+ km... I shot three (3) consecutive sights of SUN Lower Limb (LL):
(1) UTC 15:09:52 - Hs 39° 28.6'
(2) UTC 15:11:04 - Hs 39° 40.0'
(3) UTC 15:15:41 - Hs 40° 02.0'
AVG UTC 15:11:32 Hs 39° 43.5'
My sight reduction shows I was out by ~ 3.2' towards...
The actual sighting experience shooting off-hand was I imagine what it feels like to have Parkinson's Syndrome... shaky and very frustrating, but more especially because to center the inverted image in your scope, the direction you wish it to go is completely counter-intuitive; e.g. if the Object is in the upper left of your view through the scope, you carefully and shakily ease the sextant down and to the right...
The following extract from the 1997 Admiralty Manual of Navigation Vol 2 suggests that the inverting scope was used at sea by experienced navigators, but was probably a hold-over from olden times and likely omitted from the current editions, as they no longer use that equipment.
File:
