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: Extremely poor conditions??
    From: Alexandre Eremenko
    Date: 2012 Mar 21, 14:43 -0400

    David,
    What I read suggests that the rays near horizon can be indeed bent
    in any direction, towards Earth or away.
    The question HOW MUCH can they be bent.
    
    Nothing that I read so far suggests that they can be bent THAT MUCH as
    we observed.
    
    Alex.
    
    On Wed, 21 Mar 2012, David Fleming wrote:
    
    >
    > Yes, I agree as my prior statement retracted the statement about equality.
    >
    > Still terrestrial refraction results in rays with a center of curvature
    > toward the earth.
    >
    > Additionally the increase in air density due to cooling effect of the water
    > will increase that curvature further raising the apparent position of the
    > horizon giving the results obtained in your meazsurements
    >
    > On Wed, Mar 21, 2012 at 1:24 PM, Alexandre E Eremenko <
    > eremenko---purdue.edu> wrote:
    >
    >>
    >> David,
    >>
    >>
    >>  That is the sun LL is seen 30 min higher in sky than it is.
    >>>
    >>
    >>  This means that usual conditions also raise the apparent horizon by the
    >>> same 30 mins or the visible horizon is further than the geometric horizon.
    >>>
    >>
    >> No. The first statement does not imply the second. Just look at the
    >> Almanac table for the dip.
    >> The reason is that the ray from the Sun travels through the whole
    >> atmosphere (so it has plenty of time to get distorted by 30')
    >> But the ray from the horizon travels to our eye only few miles.
    >> So this second ray is distorted much less.
    >>
    >> As the dip table in the Almanac shows.
    >>
    >> Alex.
    >>
    >>
    >>
    >>
    >>
    >>
    >
    >
    >
    >
    > View and reply to this message: http://fer3.com/arc/m2.aspx?i=118450
    >
    >
    >
    
    
    
    

       
    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