# 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: A, B & C Azimuth Tables Questions
From: David C
Date: 2017 Feb 21, 00:26 -0800

According to Blackburne the ABC tables can be used for more than calculating azimuth. Here are the claimed uses:

• Find azimuth
• Find error in long due to an error in lat when working a time sight.
• Find initial great circle course.
• Find great circle distance
• Find meridian of GC vertex
• Find latitude of GC vetex.
• Find a succession of points on a GC to plot track on a Mercator chart.
• Find the long of the point of tangency of the arc of a GC with the limiting parallel of lat (as in NZ to Cape Horn)
• Windward GC sailing.
• Identify an unknown star.
• Given lat, dec, hour angle find the alt.     ...............Use for intercept method???
• Find reduction to the meridian (in conjunction with ex-meridian tables)
• Find hour angle of maximum altitude with A and B tables  .............Investigate this?

The calculation of azimuth and the calculation of initial GC course are the only uses I have put the ABC tables to. I have marked two other uses that IMHO deserve further investigation. When working an intercept I determine the azimuth with the ABC tables. If I have interpreted what Blackburne has written correctly then I can also calculate Hc by ABC tables. i.e. the ABC tables and the NA are the only volumes I need for astro. It seems too good to be true. I suspect that the interpolation required and the low precision would make this method impractical except in an emergency.

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)