Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding

Compose Your Message

Add Images & Files
    Re: A little space navigation
    From: Frank Reed
    Date: 2018 Oct 8, 11:44 -0700


    You're absolutely correct that we can determine altitude from this image (even if it's photo-realistic artwork --always possible!). As you  have described, the trick, which I had hinted at in my original posting of the image, depends on a perspective effect. When you're closer to a planet, the proportion of the apparent disk of the planet occupied by features at the center of the disk (like North America in this case) increases. This is entirely independent of the total angular size of the planet and therefore independent of magnification. It's only useful when the observer is nearer than a few planetary diameters. This diagram may help others to see what's going on...

    Frank Reed


    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