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: David Fleming
    Date: 2012 Mar 21, 13:33 -0400
    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---.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.






       
    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