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
    I need some help please
    From: Geoffrey Kolbe
    Date: 2006 Dec 09, 09:00 +0000
    This list seems to tolerate attachments these days, so long as they are "small"

    Why are you throwing away half your data and just using Alpheratz, Venus and Rasalhague?

    Here, for what it is worth, is my analysis.

    First, look at the Moon-Rasalhague position lines. They are almost parallel, but about ten minutes apart (in the area of interest) and the bodies are opposite each other. This indicates some systematic error of about +5 minutes, which might be index error or an error in dip due to some atmospheric effects. Anyhow, draw a line right in between these position lines to bisect them and to  amalgamate the Moon-Rasalhague sightings. This takes out the systematic error in these sightings.

    Now look at the Altair-Kochab pair. They are roughly opposite each other, so you can bisect these two position lines, which will take out the systematic error from these sightings.

    Now all you have left is the Venus-Alpheratz pair. These bodies are both in the same quarter of the sky, so you cannot take out the systematic error by combining them - but bisect them anyway, so forming a third amalgamated-position-line which runs pretty much exactly North-South. However, note that from the Moon-Rasalhague position lines, the systematic error seems to be around +5 minutes. Your sextant is reading about 5 minutes too high. So, assume this systematic error is present for all your sightings and move your Venus-Alpheratz amalgamated position line 5 minutes to the West.

    Now you have three amalgamation position lines all crossing at the same point at around 40N17,153W13. That is where you are - roughly.

    Geoffrey Kolbe

    ----- Original Message -----
    From: Guy Schwartz
    To: Navigation Mailing List
    Sent: Friday, December 08, 2006 10:35 PM
    Subject: I need some help please

    First I hope that people do not freak out about the attached PDF file.
    I think PDF are gennerally regarded as safe.
    Ok on to the questions if you look at the plotting sheet I scanned, there are six objects. Maybe plotting 6 objects is too many. This plot is exercise 3-2 from the book 100 problems in celestial navigation.
    My fundamential question is which sights form the enclosure of my position? I'm thinking Alpheratz, Venus, and Rasalhague, however I have no basis as to why these and not any others.
    Thank you for your help and hopefully the PDF file has not pissed anyone off.
    I know people are skittish about attachments.

    To post to this group, send email to NavList@fer3.com
    To unsubscribe, send email to NavList-unsubscribe@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