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
    Name or NavList Code:
    Refraction formula
    From: Paul Hirose
    Date: 2000 Sep 25, 10:25 PM

    The tables I posted showing the effect of refraction on angular
    separation used the refraction values from the table in the Nautical
    Almanac. For some reason it never occurred to me that the Almanac
    would have a formula I could program into my calculator, but it does:
    R = 1 / tan (H + 7.31 / (H + 4.4))
    H is the non-refracted altitude. R is the number of minutes to add to
    H to obtain apparent (refracted) altitude. The formula is for standard
    conditions of 10 degrees C and 1010 millibars. Be sure to observe
    correct order of arithmetic operations: divide 7.31 by (H + 4.4), then
    add H and take the tangent.
    Of course the formula is an approximation; note that refraction is not
    exactly zero at H = 90!
    I rewrote my calculator program to use this formula and recomputed my
    tables. The differences were trifling.

    Browse Files

    Drop Files


    What is NavList?

    Get a NavList ID Code

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

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

    Email Settings

    NavList ID 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