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: September Equinox computation
    From: Jay Borseth
    Date: 2002 Sep 24, 23:11 -0700

    Sorry, pilot error!
    
    The result I gave earlier using Pocket Stars was totally wrong.  I
    stupidly just searched for a declination of 0, without simultaneously
    searching for SHA=180 deg.
    
      The new, improved Pocket Stars result is: 4:55:26 AM GMT on 23 Sep
    2002, crossing at E 104d16.8'.
    
    I don't know for sure, but I'm guessing the 2 second discrepancy could
    be due to differences in DeltaT, for which I've seen multiple different
    projections for 2005.  Values for intermediate dates such as 23 Sep 2002
    are linearly interpolated from the 2000 and 2005 data points.  Pocket
    Stars is using 69 seconds for 2005, but I've seen 66 seconds used
    elsewhere.
    ...
     Julian Date        Year           DeltaT
     2451544.5000000, /*2000.0000,*/   63.86,
     2453371.5000000, /*2005.0000,*/   69.0, // 66.  Alternate values from
    other sources
     2455197.5000000, /*2010.0000,*/   74.0, // 70.
    ...
    
    Jay Borseth
    
    
    > Herbert Prinz wrote:
    >
    > Hi guys,
    >
    > I was already wondering how Dan Allen could be off by more
    > than 3 minutes using Meeus' algorithm, but no way did I
    > believe that the JPL ephemeris plus Novas routines could be
    > early by 3.5 minutes, whether its all written in Fortran, C or Cobol.
    >
    > So I plug the numbers into my carefully re-written Pascal
    > version of the Novas routines using DE200 and obtain (by
    > doing what I described in my earlier message) for the time of
    > this year's autemnal equinox  4:55:24 UT1. This value has the
    > advantage that it agrees with what Meeus publishes in "Tables
    > of the Sun, Moon and Planets", as well as with what the USNO
    > thinks it should be. (see  Earth's Seasons, etc. 1992-2005
    > ). This is probably not a coincidence.
    >
    > Herbert Prinz
    >
    > >
    > > Jay Borseth wrote:
    > >
    > >   The results I'm getting put the equinox at:
    > >
    > >      4:51:54 AM GMT on 23 Sep 2002, crossing at E 105
    > degrees 9' 56".
    > >
    > >
    > > Dan Allen wrote:
    > >
    > > PS - My computations for this year put the equinox at
    > 4:52:04 AM GMT
    > > on 23 Sep 2002.
    >
    
    
    

       
    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