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
    Re: Parallax of the Moon
    From: Stan K
    Date: 2015 Feb 7, 02:47 -0500
    I asked this question a couple of days ago and I cannot believe I have not received one response.  Dozens of responses on "Irregular Quadrilateral Center" and "Japanese Sextant 1979", but none on this question.  Well, last night I was sitting on the couch watching Hawaii Five-0 when I had an epiphany.  I was using the formula on page 280 of the Nautical Almanac, PA = HPcosH+OB, where HP is the horizontal parallax, H is the apparent altitude (sextant altitude corrected for index error and dip, H = Hs + I - D), and OB is the correction for the oblateness of the Earth.  It might be said that the first part of the formula, HPcosH, is just an approximation, but it is a very good approximation.  The problem is much more basic than that.  THE FORMULA IS INCORRECT!  Now I will play Frank Reed and challenge you to tell me why.  It is really pretty simple once you give it a little thought.

    Stan



    -----Original Message-----
    From: slk1000 <slk1000@aol.com>
    To: navlist <navlist@fer3.com>
    Cc: slk1000 <slk1000@aol.com>
    Sent: Thu, Feb 5, 2015 6:07 pm
    Subject: Parallax of the Moon

    The attachment is part of an output from the USNO Celestial Navigation Data web page.  Can anyone tell me how the USNO gets a parallax value of 15.6'?  Every other source I tried got about 15.27', but 15.6' is the only one that makes the numbers agree with the Moon Altitude Correction Tables in the Nautical Almanac.

    Stan


    File:

      
       
    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