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
    Sunrise Sunset by Bowditch Table 25
    From: Greg Rudzinski
    Date: 2011 Jul 13, 19:29 -0700

    The recent discussions on time sights had me reviewing Bowditch table 25 in my 1981 vol. 2 . I was amazed to discover that table 25 not only solved for the prime vertical altitude / meridian angle but could also be used to solve for sunrise and sunset. To derive sunset it is necessary to take the complement of the latitude (90*- Lat) then re-enter table 25 using the complement as the latitude with the same declination. The (t) value will be sunrise when converted to time. Sunset will be 24:00 minus sunrise. To get exact times that match the Nautical Almanac it is necessary to adjust for the equation of time, semi-diameter, and refraction. These corrections cause an asymmetry relative to 12:00 noon which varies throughout the year. All this is new for me since I always took the tabular values in the Nautical Almanac for granted.

    Greg Rudzinski
    ----------------------------------------------------------------
    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