Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Reliable Index Correction to a Tenth Minute of Arc; WAS Longitude by lunar altitudes
    From: Bill Morris
    Date: 2010 Feb 17, 12:20 -0800


    You wrote:

    "As to the recalled difficulty with different telescopes, I would suggest that this implies a lack of parallelism between the plane of the arc of the instrument and the long axis of the telescope. "

    I think I am correct in saying that as the sextant reading approaches zero, so does the error from mis-collimation reduce. At a reading of 10 degrees, for example, Simms gives the error as only about 5 seconds for a tilt of a whole degree (an amount that should be noticeable to most people).

    I suggest that those who believe they can correctly estimate their index error to a tenth of a minute on the basis of a single estimate deceive themselves. I would invite them to estimate it thirty times in a row and if they can get the same result within a tenth of a minute each time, I will be among the first to congratulate their instrument.

    Kind regards

    Bill Morris
    New Zealand
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting Code:

    Custom Index

    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