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: Angles without a protractor
    From: Örjan Sandström
    Date: 2012 Oct 12, 11:41 -0700

    I posted an explanation while ago how to divide a circle into 3 degree segments accurate to level you can measure.
    usually this translates to, at best 0.1 degree accuracy, with a good steel ruler good divider and plenty of time and care. more on posting linked to below.

    the 1° div can be made with a verniere system but it is a bit of a cheat, you need perspex or similar transparent material and scribe lines from centre of that correspondig to 0, 3, 6, 9 and 12 degrees.
    first using 0° as "cardial" line and the others as "divisions" slide the 0° line out on top of and paralell to a "0" line on the scale you want to subdivide until 9° line is touching the next division on the circle you can now drill a hole where the 3 and 6 degree lines of the perspex vernier meet and thus pick out the 1 and 2° ticks, now repeat using 12° as cardinal, the difference should be small enough to require loupe to see if any, error should be shade less than 5% of distance between ticks in theory, but we all know practice and theory.....
    now you have a circle divided into single degrees.

    having done as posting linked and the above you can make a verniere covering 10 degrees slide this out same way until 9 lines of the original scale are covered by 10 lines of the vernier scale using 5° line as centre this way you could get down to half degrees accurately, no sadly not 1/10° as the lines are not paralell they just indicate centre between two div not 1/10.
    if two such verniers are added to a rotating arm (two verniers 180° appart) this arrangement can be used to see errors in individual division ticks so they can be corrected.
    further iterations (second time with scales 181°appart third 183°...) this should improve accuracy if care is taken, hard part is getting below 10' accuracy, for that lines need to be very fine and divisions extremely accurately cut.
    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