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: Fw: Sight Reduction by Hand you might like
    From: Hanno Ix
    Date: 2014 Jan 1, 20:29 -0800

    Alex:

    I just saw this posting of yours.

    There is EXCELLENT reasons for NOT using logarithms when doing sight reduction by hand.

    Or rather, there is EXCELLENT reasons for using the method as described in the posting g24866/.

    1. The method asks for working only with 4-digit integers. The operations are
    limited to: addition, subtraction, division by 2 and division by 4.
    NO multiplication.

    2. It requires just 2 (two!) pages of a table - much less than MT-43.

    2. It does so with an error of +-0.5 min from 0 to 90 deg. - i.e. above
    85 deg!

    3. The method will work for all combinations of declination, latitude
    and hour angles - no need to consider any special cases.

    4. It is easy do teach and to memorize.

    By comparison, the literature on CelNav with logarithms, even by acclaimed experts, contains many examples that are seriously wrong. No wonder: log methods require 6 digit calculations, cannot deal with negative angles and cannot deal with angles close to 0 and 90 degrees. Therefore one can get easily lost in the consideration of special rules that apply in those cases.

    The real "problem" of any sight reduction by hand is the "by hand" part, of course. I know because I am certainly not good at it myself. But that is where its nobility lies: the simplicity and the challenge for mental acuity and discipline.

    I wish you could spend some time to go through an example or two. I'd love to hear what you thought when you were done.

    Hanno

    ----------------------------------------------------------------
    NavList message boards and member settings: www.navlist.net/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]navlist.net
    ----------------------------------------------------------------

       
    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