# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Message:αβγ
Message:abc
 Add Images & Files Posting Code: Name: Email:
Re: Cryptic Slide Rule Formulae
From: Greg Rudzinski
Date: 2016 Jan 21, 06:16 -0800

Jim,

(6.) is the prime vertical formula used with the azimuth formula (2.) when the azimuth is near 90° or 270°.

(7.) is the amplitude formula used to determine the azimuth of the Sun when the lower limb is 2/3 of a diameter above the visible horizon.

Greg Rudzinski

From: Jim Rives
Date: 2016 Jan 20, 12:58 -0800

Hello,

My father-in-law, who sailed for years out of Huntington, LI, passed away a year ago.  In one of his desk drawers I found a 10" Sterlin Slide Rule, No. 584.  It is white plastic, not very eleborate.  (however, still beyond my slide rule skills!)  He had scratched the following 7 formulae on it.  I am just wondering if anyone would recognize the text or method he was using this rule for:

In no particular order:

1.     sin h = sin L sin d + cos L x cos d cos t

2.     sin z = cos d sin t sec h

3.     cos co-d = cos co-h cos co-L + sin co-h sin co-L cos z

4.    sin t = (sin z sin co-h)/sin co-d

5.    cos t = tan d cot L

6.    sin h = sin d csc L

7     sin A = sin d sec L

Browse Files

Drop Files

### Join NavList

 Name: (please, no nicknames or handles) Email:
 Do you want to receive all group messages by email? Yes No
You can also join by posting. Your first on-topic post automatically makes you a member.

### Posting Code

Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
 Email:

### Email Settings

 Posting Code:

### Custom Index

 Subject: Author: Start date: (yyyymm dd) End date: (yyyymm dd)