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: Index Error - Comparison to SD per Nautical Almanac
    From: Modris Fersters
    Date: 2020 Nov 25, 12:39 -0800

    Hi, Jim!

    As I understood, you did following steps:

    1. you turned micrometer untill the lower limb of the reflected image just touched the upper limb of the direct image of the Sun (see picture bellow).

    Then you wrote the sextant reading;

    2. then you turned micrometer while the lower limb of the direct image was in contact with upper limb of the reflected image. And again you wrote the sextant reading.

    3. Then you calculated SD: (a+b)/4; (a= reading on arc; b= 60-reading off arc).

    Example: on arc reading: 0 degrees 31 minutes;

    Off arc reading: 359 degrees 28minutes;

    SD=(31+(60-28))4=15,75’

    And this value differed from Almanac  0,2’.

     

    I have some questions:

    1) Are you sure, that your sextant had no significiant side error?   

    2)Did you take some 3-5 measurments and averaged them to get SD?

    3) What sextant did you use? High quality or cheap one; old or new? What is stated accuracy of your sextant?

    4) Are you sure that your sextant had no backlach? To avoid this error allways turn micrometer drum only in one direction.

    If your method for calculating SD was different, please write. 

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    NavList is a community devoted to the preservation and practice of celestial navigation and other methods of traditional position-finding. We're a group of navigators, navigation enthusiasts and hobbyists, mathematicians and physicists, and historians interested in all aspects of navigation but primarily those techniques which are non-electronic.

    To post a message, if you are already signed up as a NavList member, start a new discussion or reply to any posted message and use your posting code (this is a simple low-security password assigned when you join). You may also join by posting. Your first on-topic messsage automatically makes you a member, and a posting code will be assigned and emailed to you for future posts.

    Uniquely, the NavList message boards also permit full interaction entirely by email. You can optionally receive individual posts or daily digests by email, and any member can post messages by email (bypassing the web site) by sending to our posting address which is "NavList@NavList.net". This functionality is similar to a traditional Internet mailing list: post by email, read by email, reply by email. Most members will prefer the web interface here for posting and replying to messages.

    NavList is more than an online community... more about that another day.

    © Copyright notice: please note that the rights to all messages and posts in this discussion group are held by their respective authors. No messages or text or images extracted from messages may be reproduced without the explicit consent of the message author. Email me, Frank Reed, if you have any questions.

    Join / Get 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)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site