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: Peter Monta
    Date: 2014 Jul 28, 01:58 -0700
    Hi Hanno and Francis,

    I assume Peter would be happy for me to use his current scales to make an Otis King Replica for personal use?

    Sure.  There is also source code in C if you want to make modifications, though nowadays it might be better to port the thing to python and SVG.

    It would be cool to have a version with artwork much closer to the original---that way damaged scales could be replaced and accuracy improved.  The original scales leave something to be desired---they have about 0.04 percent peak error but could support 0.01 percent system accuracy if they were perfect.
    If he could generate a sin scale same dimensions as the current log scale

    I have a question about that.  If the new scale is the same as that on a slide rule (the "S" scale), then it would cover angles from 5.7 degrees to 90 degrees, that is, angles whose sine is between 0.1 and 1.  Is that acceptable for celestial navigation?  Providing yet another scale for the interval from 0.57 degrees to 5.7 degrees, as the slide rules sometimes do ("ST" scale), seems a bit much for the Otis King form factor---one additional scale seems quite enough.  Are there convenient tricks to fill in the hole from 0 to 5.7 degrees?

    Alternatively, some sort of natural-sine scale indexed from the Otis King linear scale (on the model L) might do the trick.

    that would be just like my current mini fuller cos 2 which works perfectly for all celnav calcs using the cosine formulae. This should give us a slightly more compact and easier to read “big trig Otis King”. Slightly bigger than the original, possibly more accurate, but smaller than my mini fuller 2 and not needing the magnifiers to read the scales. Should be the perfect celnav slide rule I think!

    I see your Fuller 2 has an S scale (very nice reproductions by the way), so you must already have a workaround for the 5.7 degrees issue that doesn't involve an ST scale---what scheme did you end up with?

    Hanno, you have a typo in the link---my Otis King scales are here:


    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