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
    2102-D and CP-300/U starfinder altitude/azimuth grid projection
    From: Michalis Vaidanis
    Date: 2021 Feb 23, 14:06 -0800

    After Frank Reed’s and Gary LaPook’s ideas about some modifications of the Rude starfinder (addition of twilight lines, time scales, analemma etc, here: http://fer3.com/arc/m2.aspx/Modifications-2102D-LaPook-apr-2009-g7982 and here: http://fer3.com/arc/m2.aspx/CP300U-USAF-Star-Finder-FrankReed-feb-2021-g49784) and in seeking a way to digitally reproduce the Azimuth/Altitude grids, I stumbled upon the “G.Projector” application from NASA (https://www.giss.nasa.gov/tools/gprojector/). After playing with it a bit, I managed to get grids that fit almost perfectly to the 2102-D blue templates. However, this was not the case with the CP-300/U, the grids of which extend 10 degrees below the horizon.

    For comparison, I’m attaching the G.Projector grid, along with its superimposition to the relevant 2102-D and CP-300/U templates. The G.Projector grid was produced with the following parameters: azimuthal equidistant projection, observer at 5 degrees North, azimuth and altitude at 5 degree intervals, lowest altitude at 10 degrees below horizon.

    What is not clear to me is why there is that plot difference between 2102-D, CP-300/U and the G.Projector grid, especially to the altitude parallels extending below the horizon. Are the 2102-D and CP-300/U projections the same “plain” azimuthal equidistant or the latter is tweaked somehow?

    What am I missing here? Any ideas?

    File:
    G.Projector-Grid.pdf
    File:
    CP300U-G.Projector-Grid-Comparison.pdf
    File:
    2102D-G.Projector-Grid-Comparison.pdf
       
    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