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: Star - Star Observations
    From: Douglas Denny
    Date: 2010 Mar 9, 16:17 -0800

    Might I be a wee bit pedantic George?
    Just to make it clear in case of confusion. You say:

    "Add the appropriate refraction correction, to get the apparent altitude".

    Refraction is a minus quantity always subtracted from the Apparent direction (altitude) of the light ray to give the True direction (altitude) of the light ray. (i.e. the apparent altitude is always greater than the true altitude).

    The statement above about adding the corection is correct if refraction is algebraically added as a minus quantity.

    Then find difference in hour angles (RA's) of the two stars and work out angular distance between them with spherical trig as George says.

    Terminology is usually:

    _Sextant altitude_: corrected for index error gives:
    _Observed altitude_: Corrected for Dip gives
    _Apparent altitude_: Corrected for refraction, semi-diam, irradiation, and parallax in altitude (as necessary) gives -
    _True altitude_.

    Douglas Denny.
    Chichester England.
    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