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: Refraction at the horizon.
    From: Marcel Tschudin
    Date: 2008 Mar 19, 21:07 +0200

    A reply to George's comment:
    
    Before I mentioned "ducting" only in the context of verifying the
    program. I tried to show that for verifying the program we looked at
    all sorts of tricky cases. The profile used in this calculation to
    derive a transfer function for refractions at large ZDs was the very
    well behaved standard atmosphere which produces no strange anomalies.
    The only special thing in it is the observer being very high up,
    almost at the tropopause. One of the test case with which we compared
    our programs was similar, it also had the observer at 10 km height
    otherwise also a "normal" lapse rate profile. The differences we had
    were much less than those resulting from the exponential behaviour.
    
    George mentions:
    "Gravity has reduced by only one part in 300 from the surface to 10 km
    up, so it's hard to see that having much effect, except at enormous
    heights, where no air remains."
    
    The effect from gravity is expected to be larger since it appears in
    the power. I really don't know the possible reasons for it; may be
    gravity is one of them. From tests done on the program it looks like
    the effect is "real", but not knowing the cause I can't exclude the
    program. May be someone else would give try. How about you Frank?
    
    --~--~---------~--~----~------------~-------~--~----~
    Navigation List archive: www.fer3.com/arc
    To post, email NavList@fer3.com
    To unsubscribe, email NavList-unsubscribe@fer3.com
    -~----------~----~----~----~------~----~------~--~---
    
    

       
    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