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: Difference between HO 249 and USNO website
    From: Gary LaPook
    Date: 2016 May 17, 17:06 +0000
    It appears that your problem is that you used different assumed positions for tach computation. Look at your input data to the USNO website, it is different than the AP shown in block 6 of the 249 reduction. When you do that you find the Hc is 21-22.6.


    From: John Almberg <NoReply_Almberg@fer3.com>
    To: garylapook@pacbell.net
    Sent: Tuesday, May 17, 2016 9:53 AM
    Subject: [NavList] Difference between HO 249 and USNO website

    Hi there. I am wondering why the sight reduction results from HO 249 and the USNO website (http://aa.usno.navy.mil/data/docs/celnavtable.php) differ so much. 
    I've attached my own calculations using HO 249, and the results from the website. The Zn value is the same, but the Hc values are significantly different. Is this normal? Or am I doing something wrong (the most likely scenario!)
    I should mention that I took the sight using a homemade 'astrolabe', so in my own calculations I am including no altitude corrections. i.e., no dip and no SD correction.
    Any thoughts, much appreciated.
    -- John

    Attached File:

    Attached File:

    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