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: Errors in USNO celestial data
    From: Dave Walden
    Date: 2010 May 4, 12:50 -0700

    I suggest caution in suggesting errors in USNO data. Earlier the discussion seemed never about 'errors', but about 'incomplete' data. (It turned out to be a browser issue. Unfortunately, for the reasons Frank suggests, pointed out to USNO as an 'error'.)

    In the case of the delta T question, I suggest similar caution. I have made a few ephemeris calculations based on JPL 405 data. Using dT of 66.184, I get:

    Geocentric:
    RA 2-45-50.973837, Dec 16-00-59.604557 N

    Topocentric:
    RA 2-45-50.988242, Dec 16-00-54.658768 N

    (Agreeing at .01 second level with JPL-Horizons and IMCCE results. Remaining differences due to UT-UT1 and polar motion.)

    Using dT of 72.184:

    Geocentric:
    RA 2-45-50.989878, Dec 16-00-59.676789 N

    Topocentric:
    RA 2-45-51.004283, Dec 16-00-54.731003 N

    (I hope no typo's!)

    So, I don't conclude the USNO online is using the wrong dT.
    ----------------------------------------------------------------
    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
    ----------------------------------------------------------------

       
    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