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: Swing Arm Spring tension Cassens & Plath vs Astra
    From: Greg Rudzinski
    Date: 2015 Dec 11, 10:44 -0800


    Check the Micrometer worm gear spring screws. Snug them up but not too tight. Other screws can work loose also. Use a screw driver that fits perfectly to the slot to avoid injuring the screw heads.  

    Greg Rudzinski

    From: Mark Coady
    Date: 2015 Dec 10, 18:28 -0800

    I am handling a vintage 1998 Cassens & Plath Horizon sextant in effectively new almost untouched condition. 

    I notice that the swing arm spring tension is very light.  It engages reliably without any wobble...and stays in place. I see no play with light finger pressure but I was somewhat surprised at its soft engagement, as the aluminum astra has a much thicker single leaf spring as opposed to the two spring stack, and has a much more tight engagement.

    There seems no way to overstress the C & P  as the handles come together..so it seems intentional, and it lightly stays engaged.  THe brass is finer cut than the aluminum, and from my dumb mechanical engineer perspective light engagement on those delicate teeth makes a lot of sense wear wise (the lower the face pressure..lower the wear) , especially as I notice on the astra its easy to drag the worm if careless.

    I have no guidence on what rack tension should be other than no play. I wondered in the past if the Astra's face pressure contributes to rack wear on the aluminum sextant body. 

    I also wondered if it is related to the rougher finish material needing more force for precise engagement.

    Does this spring pressure observation sync up with anyone elses sextants?



    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