A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robert Eno
Date: 2014 Oct 21, 14:17 -0400
I have one of those in my collection. Very interesting instrument but based on my own observations (no pun intended), I can understand why they never took off. The description provided by Jackson from the Undersea Warfare Magazine piqued my interest and in particular, this passage:
Rather, the celestial object was viewed directly as with the true quadrant. Instead of using a plumb bob, a liquid-damped steel ball recorded the altitude of the object on a screen.
I wonder if I have an earlier version because the steel pellets in my sextant are not liquid-damped; rather they simply free-fall through a tube and onto a screen.
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Gary LaPook
Sent: October-21-14 1:16 PM
Subject: [NavList] Re: Ball Recording Sextant
I posted the manual for this sextant several years ago, try these links:
I have never seen in mentioned in any of the many flight navigation manuals that i have so I don't think it was used much in flight.
From: Jackson McDonald <NoReply_McDonald@fer3.com>
Sent: Tuesday, October 21, 2014 3:31 PM
Subject: [NavList] Ball Recording Sextant
This explanation of the USN ball recording sextant appeared in Undersea Warfare magazine:
The invention of the ball recording sextant. It is ironic, and perhaps fitting, that the final form of the sextant – an instrument for measuring angular distances used especially in navigation to observe altitudes of celestial bodies (as in ascertaining latitude and longitude) – was not a sextant at all but a much earlier ancestor, the true quadrant. Developed for use at night when no horizon was visible, the recording “sextant” used no reflecting mirror. Rather, the celestial object was viewed directly as with the true quadrant. Instead of using a plumb bob, a liquid-damped steel ball recorded the altitude of the object on a screen. A drum micrometer was used to determine the precise altitude reading.
Because of its size, ease of use, and nighttime capability, the recording sextant found favor with airplane navigators, leading to “aircraft sextants” built on the same principle. Numerous examples still exist for the collector’s choosing at relatively inexpensive prices.
Have any of you used such a sextant? How did it perform, especially at night?