NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Longhand Sight Reduction
From: Hanno Ix
Date: 2014 Nov 17, 20:35 -0800
From: Hanno Ix
Date: 2014 Nov 17, 20:35 -0800
Gentlemen,
I am curious about the history of sight reduction. So, can anyone of you tell me if the Royal Navy made attempts at all to standardize sight reduction ? How about the US Navy and others?
The advantages of standard procedures in training, documentation, quality
checks etc. must have been so obvious. On the other side, serious disagreements about the coordinates of a certain locations have occurred and were discovered. As an example take Pitcairn Island. Of course, the possibly tragic consequences of erroneous sight reduction were never doubtful, also.
From what I found they did not do any standardization. If so, why?
Also does anyone know what their position was as to angular resolution?
H
On Mon, Nov 17, 2014 at 7:26 PM, Greg Rudzinski <NoReply_Rudzinski@fer3.com> wrote:
Thanks Bruce and others for complements and encouragement on the various Doniol sight reduction methods and modifications.
The original Doniol cosine haversine formula is an excellent trig calculator alternative for reductions. The haversine Doniol formula is an excellent option for longhand table reductions.
Good luck with your AH Bruce and let me know how your reductions compare.
Greg Rudzinski
From: Bruce J. Pennino
Date: 2014 Nov 17, 09:20 -0500Hello Greg, Gary and Hanno and others,Doniol sight reduction seems quite innovative......well done and most interesting. Now that you’ve posted a couple of examples, I’ll give the method a try (on some cold wintry evening). I usually use two methods whenever I do a reduction, just so I don’t get rusty in other methods.My recent favorite is still Weems 1927 LOP Book (1943 version) followed by H. O, 249 and hand calculator.This past weekend , for the first time, I used my USN AH No. 8 ( a mercury AH with a triangular hood) for a noon latitude sight. The wind was really blowing but the mercury was so still. Even though I rushed through the sight, the sun was earlier than I anticipated, my result was within 1 minute of arc of my actual location.I’ve compared results with Hg AH and my mirror AH ( using a cheap Empire torpedo level and ordinary mirror glass ) and my results are always within a couple/few of minutes of arc. One of these days I’ll use the first surface mirror and Hg AH.Again, thanks for all of the work. Best wishes to all.
Bruce
