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
    Polaris - changes in SHA and Declination
    From: David Shoemaker
    Date: 2019 Feb 22, 07:59 -0800

    I thought I understood star motions – my thinking was that they are basically motionless, compared to each other, in our sky, except for long term motions such as axial precession and proper motion. After working with some Polaris sights and looking at SHA and declination for Polaris for different months, I noticed that there appears to be annual oscillations with the SHA and declination of Polaris, that are somewhat out of phase with each other. I graphed the changes using data from https://aa.usno.navy.mil/data/docs/geocentric.php - Apparent Geocentric - and it seemed to verify the annual oscillations. My earlier thinking was that any changes in SHA and Dec of any star would be constant in either a positive or negative direction throughout the year, such as changes from proper motion. I know these small changes aren’t enough to be of concern in celestial navigation, a few seconds of arc, but I am wondering - Is Polaris close enough to Earth that our planet’s annual motions around the sun cause annual, cyclical changes to the SHA and Declination of Polaris ? 

    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