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: A guide to AH use
    From: Norm Goldblatt
    Date: 2014 May 17, 11:36 -0700

    Not familiar with sextant oculars, but all have a specific eye-relief spec. This is where the your eye pupil should be for maximum field of view and most comfortable accommodation. The feature called 'long eye relief' implies that glasses wearers can still place the pupil at the optimum distance. If your glasses prescription has negligible cylinder, then, you don't need to wear them as the position of the ocular can be adjusted so that the image is at a comfortable distance for you to focus.

    It's easy to determine the eye relief by simply looking through the ocular from a few inches away. As you move your eye closer, the circular aperture (exit pupil) will get bigger until you see only the circular shape of the other end of the ocular. Your pupil is now at the designed distance from the ocular. It's just like looking through a keyhole. You see more and more the closer you eye comes to the keyhole. Keyhole=exit pupil of ocular

    If you have astigmatism, you will see a point as a line. If the line is horizontal, they, heck, that's a good thing, as your vernier acuity will aid in aligning the two objects horizontally. If you can't fix it, feature it. Isn't there a cylinder add-on that smears the image horizontally for easier alignment? I thought I read it on this site.
    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