NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Brown-Nassau CN Plotter
From: Gary LaPook
Date: 2014 Nov 21, 00:02 -0800
From: Francis Upchurch <NoReply_Upchurch@fer3.com>
To: garylapook@pacbell.net
Sent: Thursday, November 20, 2014 11:21 PM
Subject: [NavList] Re: Brown-Nassau CN Plotter
From: Gary LaPook
Date: 2014 Nov 21, 00:02 -0800
Celnav was used by all the transoceanic airlines through the 70s' and some into the 80's. The U.S. Air Force though the 90's and even after 2000 for some specialized units so in flight celnav did not lose its importance after 1945.But, HO 249 had been competed and the Air Almanac so the computations were standardized and not too difficult. And you still needed the Almanac with any method even the Bygrave.
gl
From: Francis Upchurch <NoReply_Upchurch@fer3.com>
To: garylapook@pacbell.net
Sent: Thursday, November 20, 2014 11:21 PM
Subject: [NavList] Re: Brown-Nassau CN Plotter
Hi Sam,
The Brown-Nassau is not really a plotter at all (incorrectly called this at the SI) It is really a graphic circular slide rule for working out Hc and Az from given values of Lat, LHA and dec. Much quicker than using cosine formula, log tables etc , more compact than books of reduction tables and potentially much easier in a small plane that it was designed for. Not sure why it wasn’t made standard in USAF and RAF, but maybe Celnav not so important after 1945? Not sure what Gary thinks?
Either way, this thing is now very rare apparently and in danger of extinction! (only one located so far is in the SI and that might be out
“on loan” . Oh dear!). I’ve decided it is therefore my solemn duty to build a working replica, hopefully using accurate scans/photos of the SI original.
Best wishes
Francis
