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: Peculiar box sextant
    From: Luc Van den Borre
    Date: 2022 Sep 20, 15:02 -0700

    Joe Wong wrote:
    Came across this rather interesting piece on an online auction lot, and am trying to figure out the purpose of this instrument.

    https://www2.humboldt.edu/scimus/RefracExhibit/SpecDesc/ZeissSugar_oil.htm
    It's a refractometer. The small cylinder contains two prisms. You open it up and put a drop of e.g. grape juice (if you're making wine) between them. The higher the concentration of sugar in the water, the more a light beam going through it bends.

    https://en.wikipedia.org/wiki/Abbe_refractometer
    The mirror is for directing light from a sodium lamp through the sample. Sodium light has a single frequency so gives a nice sharp readout (refraction also depends on wavelength). There's a precise scale engraved on the glass under the eyepiece, invisible in the picture. The four rounded stubs on the small cylinder are attachments for rubber tubing to supply water, to bring the sample and the prisms to a required temperature (since refraction also depends on temperature).

    I'm not sure how the 0-180 adjustment on top of the alidade works. I guess it's used when calibrating the instrument for work with different solutions. "It has a revolving triple-prism compensator, like that in the Dipping refractometer, which is adjusted by a lever on the alidade.", says the first website I linked to. (Does that 0-180 scale span 36 degrees? Nice 5 to 1 ratio.)

    Cool but you can't navigate with it so meh.

    Luc

    File:


       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a 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