NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Another "emergency navigation" sight reduction method
From: Gary LaPook
Date: 2015 Jul 13, 08:53 +0000
From: Hanno Ix <NoReply_HannoIx@navlist.net>
To: garylapook@pacbell.net
Sent: Sunday, July 12, 2015 12:16 PM
Subject: [NavList] Re: Another "emergency navigation" sight reduction method
The cot() scale - partially shown in the attached picture - proceeds around 45 deg in steps of 10 arc min. So in this area of the scale any visually interpolation of 2 out of 5 without further reference is rather subjective. And this is the reason of my statement above. It could very well the biggest error component of your design!
That actually is a shame. By re-designing the set of marks you are using and including marks for 2 min steps ( e.g round dots ) you could increase the utility of your Flat Bygrave significantly. From my experience with making scales this is not too difficult, there is sufficient space for them.
H
From: Gary LaPook
Date: 2015 Jul 13, 08:53 +0000
In fact, the entire cotan scale from 10 degrees to 80 degrees is marked in ten minutes steps and it doesn't seem to affect the accuracy at all. And look at the cosine scale, part of it is marked in whole degree steps, still no problem. You get a sense when working with it that some things have very little effect on the final answer. Think about using a normal ten inch slide rule to do the sine-cosine computation. Even though some of the inputs might be in the the end of the cosine scale where it is marked only every whole degree it is easy to get results of much greater accuracy.
gl
From: Hanno Ix <NoReply_HannoIx@navlist.net>
To: garylapook@pacbell.net
Sent: Sunday, July 12, 2015 12:16 PM
Subject: [NavList] Re: Another "emergency navigation" sight reduction method
Gary,
your claim of 2 minute or better accuracy is hard to contradict - and equally hard to confirm.It also would make it possible to prove your claim.
On Sun, Jul 12, 2015 at 6:26 AM, Gary LaPook <NoReply_LaPook@navlist.net> wrote:
The cotan scale on my flat Bygrave is only 10 inches long by 7 inches high and I get 2 minute or better accuracy. The cosine scale is smaller. They each fit on standard 8 1/2 by 11 inch paper and clear plastic sheets.gl
