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
    or...
       
    Reply
    Re: Longitude by unequal altitudes - Brent
    From: David C
    Date: 2020 Jul 12, 22:30 -0700

    Lars wrote

    you should not be totally confused. The last term's numerator is clearly 620 seconds of arc, the altitude difference. In the denominator you have a constant of 2, times C which is given as 1.54 (seconds of arc)/(minutes of time)2, times (I-g) given as 77.5 minutes of time. Now 620 / (2·1.54·77.5) = 2.60 and the dimension becomes minutes of time, or 2m36s. I guess there is an explanation somewhere in Brent of the dimension of C as given in Table III.

    Thanks. it now makes sense. In an example I have worked the correction was 3.02 minutes of time. The easiest way to convert that to min and sec is to use the sexigesimal key on the calculator which gives the answer  3 min 1 sec. What confused me was that the calculator displayed this as 3° 1'  because the calculator interprets the input as 3.02°. But the input is 3.02 min of time so the answer is in min sec of time. Obvious!

    To summarise the sighst, comparing the results with my GNSS position........

    Noon sight in error by 0.4'.

    Ex-meridian LHA 9min 28 sec am error 0.3'

    Both these errors can be explained by my use of a sextant without optics.

    The longitude was determind by sights at LHA 22 min am and 17 min pm. The longitude was 8.5' in error.

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    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:

    Email Settings

    Posting 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