Welcome to the NavList Message Boards.


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

Compose Your Message

Add Images & Files
    Re: Hc formula difference why?
    From: John D. Howard
    Date: 2017 Nov 21, 17:35 -0800


    Think logarithmns and negative numbers.

    Not so long ago if you wanted to multiply or divide you used log tables ( or slide rules - same thing ) but there are no logs for negative numbers.

    The work-around was to work in positive numbers and then have rules like " If same name, subtract; if contary name, add".  By using mederian angle, T, and not GHA you could limit angles to 0 to 90 d.  Another work-around was the weird trig functons like haversine where there are no negative numbers.  We, today, think nothing of South dec being negative or West long being negative but still, I for one, must rember to ADD when subtracting a negitive number.

    The " ~ " was used with some rule - usually when to add or subtract.  Like many have pointed out, the formulas are the same.

    John H.

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting Code:

    Custom Index

    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