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: Time Sight usage
    From: Lars Bergman
    Date: 2013 Jan 15, 07:06 -0800

    Robert wrote:
    "As for the GHA of each star, it looks like he precomputed Aries for 18:17:00 Z added in the SHA, then subtracted 275º and left the remainder as the first number: 51º 49'4 Sirius, and 38º 23'4 Procyon"

    This was all I needed to figure it out (I guess ...). My explanation:

    The observer looked up GHA Aries from the NA at the preceding midnight, i.e. February 23, 0h GMT. Should be something like 152º 33'1, then added SHA for each star. For Sirius this gives 152º 33'1 + 259º 16'3 = 51º 49'4 which is the first line, i.e. GHA Sirius for 0h.

    Now, 275º is the Aries increment for 18h17m, at a rate of 15º 2'46 per hour. And 6'8 the increment for the remaining 27s. Resulting sum is GHA Sirius for 18h17m27s.

    Roberts conclusion "notice that for the Procyon sight 14 minutes later (ignoring seconds), he adds 3º 30'6 to 275º to get 278º 30'6. " is correct.

    Lars 59N 18E
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com

    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