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: How height affects sun altitude
    From: Gary LaPook
    Date: 2018 Jun 5, 15:06 -0700

    Well, yes it does happen. The measured altitude with the sextant using the sea horizon will be 90° 55.7'. That is the sextant altitude, Hs. So when using this sight you then apply the normal corrections, any index error, IC, and then subtract the dip of 55.7'  to produce the Ha of 90°. You then apply refraction correction which is zero for an observation of 90°. You then apply semidiameter of 16' (plus for a lower llimb observation)  so the observed altitude is, indeed, 90° 16'. If it was an upper limb then the Ho would have been 89° 44'. If this doesn't make sense to you, the limb is directly above you and 90° from the horizontal and the center of the sun is displaced 16' from the limb so 90° 16' from the horizon in one direction. Or you could turn around and take the observation from the opposite horizon and measure from there.  


    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