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
    Name or NavList Code:
    Email:
       
    Reply
    Re: Refraction near the Horizon ? Observation vs. Calculation
    From: Brad Morris
    Date: 2013 Apr 11, 17:46 -0700

    Hi Frank

    In your posts, you explained that geometric dip, in minutes, can be derived from 3438sqrt(2h/R) into the form dip, minutes=1.06sqrt(h).

    You then stated that geometric dip did not match the Nautical Almanac's version of refracted dip,minutes=.97sqrt(h,feet), giving a nice history lesson in marketing Navigation Tomes. I actually though that was neat.

    I responded that the geometric form of 3438sqrt(2h/R) could be made the refracted form by dividing R by (1-k), k=.164. That this unified all the equations. Made them all produce the same result.

    Here's the funny part. If I multiply 1.06 (the geometric dip constant) by the square root of (1-.164), I get 0.96919 or if you want just two decimal places .97 (the refracted dip constant). Hmmm, now why would that be?

    So it seems that we are actually in mathematical agreement, although the starting point was begun in my confusion. The equations have clearly been resolved to my satisfaction.

    Thanks for hanging in there!
    Brad


    ----------------------------------------------------------------
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com
    ----------------------------------------------------------------

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

    Name:
    (please, no nicknames or handles)
    Email:
    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:

    Email Settings

    NavList ID 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