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Re: New compact backup CELNAV system
From: Brad Morris
Date: 2009 Feb 25, 16:53 -0500

This problem does not exist on a “real” Bygrave because the cylinders are stiff and remain concentric with each other. I do recognize the difficulty in getting the scales mounted and keeping them referenced to each other when going through the zig-zag pattern of solution.

I think that local distortions of the one scale to the other will clearly result in errors. Slide rules in general work when the one logarithmic scale is referenced to another logarithmic scale. Distorting one or the other cannot be permitted. NSG21 is absolutely correct.

I remember being the last class to take slide rule instruction in High School. When you use a slide rule today, most people think of it as black magic and have no idea how it works. Further, the electronic calculator leads young engineers to give me as many decimal places as their calculator does, without judgment as to the meaning of those digits. Empty resolution without addition to accuracy.

Best Regards

Brad

From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Gary LaPook
Sent: Wednesday, February 25, 2009 4:39 PM
To: NavList@fer3.com
Subject: [NavList 7430] Re: New compact backup CELNAV system

I haven't seen the problem you mentioned. I sealed the Cotangent scale in normal plastic protection sheets (about one buck each at Fryes) used for protecting documents which are quite rigid. I will experiment with bending the scale and working a sample problem and get back to you.

gl

--- On Wed, 2/25/09, nsg21@hotmail.com <nsg21@hotmail.com> wrote:

From: nsg21@hotmail.com <nsg21@hotmail.com>
Subject: [NavList 7427] Re: New compact backup CELNAV system
To: NavList@fer3.com
Date: Wednesday, February 25, 2009, 9:47 AM

I would like to share some experience in using this (transparency over printed)

style of the slide rule. The surface it is placed for calculation MUST

 BE

ABSOLUTELY flat. Even small warping of the surface (such as normally found on

small plastic tables) leads to big errors in calculations.

  

  

  

From: glapook---NET

Date: Tues, Feb 24 2009 12:06 pm

> There are often posts on the Navlist regarding using celestial as a backup

to

> GPS and finding a simple way to do this. I think I have found a method

that

> is simple, self contained, takes up little space, needs no almanac or

sight

> reduction tables 

...

  

  

  </table

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