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: Longhand Sight Reduction
    From: Greg Rudzinski
    Date: 2014 Nov 12, 08:11 -0800


    I am in total agreement with you on avoiding interpolation where possible. Two thumbs up on the 2' table :)  A few additional benefits of the haversine Doniol table. There are no special rules for L+d > 90° or LHA Meridian Angle > 90° and the majority of observations (especially the Sun) can be reduced from the same side of the haversine table vs. page turning of other methods. After a week of trials it has become clear that this is the best short table sight reduction method that uses the DR position as the assumed position. I have a shelf of sight reduction tables that will now be collecting lots of dust ;-)

    Greg Rudzinski

    P.S. The 8" circular slide rule does almost as good a job on the multiplication step as the Ottis King.


    From: Francis Upchurch
    Date: 2014 Nov 11, 23:35 -0800

    Many thanks Greg,

    My original confusion resulted from missing Hanno's posting of Nov 5th re the Hv only formula. Now I've found it. Congratulations to Hanno for this and his 2'Hv table which I find eaiser to use than your 10' table.(I keep making mistakes with interpolation).

    I have test driven your e.g. using the Doniol, and compared it to Bygrave, and other slide rules (using cos formula, not Doniol).

    Please see attachments if interested.

    I'll certainly put your/Hanno's Doniol (Hv) into my minimalist crash bag, but also the Otis King+sin table.

    If space is not a problem, I still prefer the Bygrave, with my prototype minifuller 2cos  a close second.

    Keep up the good work both.

    Best wishes

    Francis Upchurch

    Attached File:


    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