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: DIY long-term almanac for calculators
    From: Bruce Cutting
    Date: 2018 Jan 17, 13:18 -0700

    Any chance getting you to share the code  I hve a TI-89 - believe they are
    code compatible (basic)
    
    
    > On 2018-01-15 8:18, Tony Oz wrote:
    >> I programmed my TI-83 to do the computations as per Chapter 15 of
    >> Henning Umland's excellent "Short Guide to Celestial Navigation", where
    >> the author warns on the accuracy:[BEGIN QUOTE]
    >> The maximum error of GHA and Dec is about ±0.6'. Results have been
    >> cross-checked with Interactive Computer Ephemeris 0.51 (accurate to
    >> approx. 0.1'). Between the years 1900 and 2049, the error was smaller
    >> than ±0.3' in most cases (100 dates chosen at random). EoT was accurate
    >> to approx. ±2s. In comparison, the maximum error of GHA and Dec
    >> extracted from the Nautical Almanac is approx. ±0.25' (for the sun) when
    >> using the interpolation tables. The error of SD is smaller than
    >> ±0.1'.[END QUOTE]
    >
    > I coded his formulas in a program which compares them to the JPL DE431
    > ephemeris at 1000 random times in the 21st century. It generally
    > confirms Umland's accuracy claims. For Sun apparent place, semidiameter,
    > and equation of time the program calculates an accuracy statistic for
    > the whole set (square root of the mean squared error) and also remembers
    > the single worst result.
    >
    > Apparent place error is the separation angle between a vector to the Sun
    > calculated from the Umland formulas and a vector from the JPL ephemeris.
    > It therefore combines the errors in RA and declination into a single
    > number.
    >
    > .33′ apparent place RMS error
    > .95′ max
    >
    > .006′ semidiameter RMS error
    > .007′ max
    >
    > .90 s equation of time RMS error
    > 2.95 s max
    >
    > View and reply to this message:
    > http://fer3.com/arc/m2.aspx/DIY-longterm-almanac-for-calculators-Hirose-jan-2018-g41198
    
    
    

       
    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