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: Dipmeter: was [NAV-L] Wires, back sights and collimation
    From: Alexandre Eremenko
    Date: 2004 Dec 1, 22:10 -0500

    Frank,
    
    On Wed, 1 Dec 2004, Frank Reed wrote:
    
    > Myself, I can't think of any technical reason. Can you? I suppose simple
    > conservativism of design would be an explanation...
    
    The only explanation I can think about is that the inverting scope
    is used for taking large angles. (I am not saying that they
    were thinking of lunars, but probably large horizontal angles
    between the objects on the shore. The arc of this sextant
    permits measuring angles to 140d.
    Now when taking such large angles, very small collimation
    error becomes relevant.
    So they did everything to reduce it.
    a) added the wires
    b) added the collimation screws.
    Alex.
    
    P.S. By the way, when taking large distances, I always
    have an error which varies between 0.3 and 0.7
    which I cannot explain. It occurs permanently, and I can
    correct for it if I wish. But what is the reason for this error
    I do not understand. Here is my typical recent lunar:
    
    Dec. 1, GMT 15:32 Lat 40d27.2N, Long 86d55.8W Sun-Moon IC=0.
    Temperature 33F Pressure 30.1 Reducing with Frank's calculator,
    last column is the error.
    
    15:43:46    127d12.2     0.8
    15:46:15    127d10.8     0.6
    15:47:40    127d09.8     0.3
    15:49:45    127d09.1     0.7
    15:53:28    127d07.2     0.7
    
    The average error is 0.6, and maximal
    deviation from this average is 0.3
    
    This 0.6 overshot occurs in all my
    measurements of distances larger than 90.
    But what is this?
    Repeated measurements of the index error
    give zero. Well, never more than 0.2.
    All my attempts to measure collimation error
    also give zero.
    
    So this is either some kind of
    "personal equation/irradiation"
    or some problems with the arc excentricity.
    
    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