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: ? ? ? Re: Dip uncertainty
    From: Bruce Stark
    Date: 2004 Dec 6, 19:06 EST
    Alex,

    You said: "Its another matter that from 20 miles, no matter how powerful
    your scope is (and assuming ideally transparent atmosphere,
    better no atmosphere at all) you will not be able to see the horizon
    THROUGH your prism. What you will see is some spot of the sea surface
    near the prism."

    I realized, too late, that instead of a prism I should have specified a plate of glass with just enough difference in parallelism of surfaces so that a ray coming from the horizon (say 2' below horizontal) would be bent down 2' in passing through it, and come out of the glass horizontal to the earth at that point. At the buoy, looking through the glass, you'd see the horizon 2' above its true place. Looking through the glass from 20 miles away you'd see the horizon very close to its true place.

    Bruce
       
    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)