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
    Sextant experiment
    From: Modris Fersters
    Date: 2021 Jun 12, 07:34 -0700

    Hello everyone!

    I would like to offer an experiment with metal sexant. I am interested in such a problem: is your metal sextant affected by the tilt angle of the sextant. This problem is not actual for usual celestial observations where the sextant is positioned verticaly. But  while taking lunar distances sextant can be tilted in any angle.  I own only one sextant, therefore I have no opportunity to check other sextants. But I am sure that many NavList members own metal sextants. And an idea came to my mind: maybe you can help me by testing your instruments and by posting your results.

    This experiment will not take much time. It will be the usual finding of Index Correction by the Sun. But unusual will be the position of the sextant.

    Just do following steps:

    1) do the usual adjustments and reduce index error to 1…2 minutes of arc ;

    2)choose filters for index miror and horizon miror (or use one filter on telescope). Do not change filters during experiment!

    3) tilt your sextant horizontaly with its face upwards (see picture).

    4)fix index arm at position around -1 degree (off arc). Then turn micrometer only in one direction (in the direction of increasing angle). Make direct and reflected Sun images in contact. Read down micrometer. Important: for off arc angles (below 0 degrees) write down micrometer reading as it is. Dont  recalculate the angle as negative value. If micrometer shows 32 minutes, then write 32 (not 60-32=28).

    5) continue to turn micrometer in the same direction and again make direct and reflected images of the Sun in contact. Read the micrometer.

    6) Repeat this procedur at least 5 times.

    7) then do the same procedure, but with sextant facing downward.

    As a result you will  have 5 pairs of readings when sextant is with it face upward, and 5 pairs of readings when sextant face is oriented downward (two small tables; see picture).

    From these results I will calculate two average index corrections  dependent on sextant position.

    My sextant SNO-M shows constant difference between these two average index corections. I am very curious to find whether your sextants have the same peculiarity.

    I will be very grateful to receive your results. And please write your sextant model name and the date of observations. If I receive any results I will post the summary later.

    Thanks!

    Modris

    File:
    sextant_experiment.pdf
       
    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