Welcome to the NavList Message Boards.

NavList:

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

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: CN Humor....speaking of humor..the source of the quoted formula...
    From: Mark Coady
    Date: 2015 Dec 3, 21:26 -0800

    Sean,

    I have it written in my notebook from my early days of reading everything in sight learning on my own.....I forget who I pilfered it from.

    Checking it, I have an 1868 editon of Bowditch and if I go to the augmentation table it has a range of values from 0 augmentation  {at} 0 alt to 16 seconds augmentation  {at} 90 alt.  (which =.2667 {at} 90 degrees) (sin value of 1) 

    From there a check with the sin of the altitude say at 45 degrees:   (bowditch augmentation 11 seconds=.183)  (my filched formula .26 sin 45 =.184)  so it matches within any rational quest the Bowditch table.

    I note the Bowditch table is an approximation, Augmentation  varies with a horizontal paralax, and the Bowditch table i believe is calculated on the average of HP {at} about 57.7 HP  which comes out to the .26 number which varies a bit with rounding.  

    My notes comment that actual augmentation factors vary from .299 at an HP of 61.4 to .230 {at} at an HP 53.9'.  (A min max scenario).  which gives me an average of .26 by inspection (hence my use of it)  Round to 1 decimal and back to old .3 agian.

    Based on what we are doing in a lunar as I understand it, heck its close enough. 

    I recall the whole calculation is based on the 27.24% ratio SD to HP, and the factor of added size for the radius of the earth in NM 3438? (based on using the 21,600 circ.)

    Someone cooked up a rule long ago that adds a bit of perspective on all my futzing with extra decimals....  Measure with a micrometer,  Mark with chalk, Cut with an axe.......   

     

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    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)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site