Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Interpolation to latitude
    From: Ark Shvetsky
    Date: 2009 Nov 8, 23:22 -0800

    L.Gray, "100 Problemsin Celestial Navigation" Problem 1-1
    "...sailiing from New York to Azores... May 13, 1993.  DR position at 0730 
    (GMT) will be 40 deg 10' N and 50 deg 15' W.  Planning for a round of 
    twilight sghts..."
    50 deg 15 ' of long is equal to 3 hr. 21 m, which we add to LMT to get GMT.
                        LMT      GMT
    Nautical twilight  0337      0658
    Civil twilight     0414      0735
    Sunrise            0446      0807..."
    Appendix B (which is "how to")
    "1. On the right-hand daily page of the almanach, enter the upper half of the 
    table (a.m) with the expeced DR latitude at the time of the twilight. 
    (interpolate for latitude, either by eye or mathematically)..... Convert each 
    LMT to GMT  by adding... or subtracting .. the time equivalent of the 
    expected DR longitude-found on the first yellow page in the back of the 
    My question is: why there is no mentioning  of interpolaion for the longitude 
    in calculating twilight phenomenon?  As I mentioned before, I think the 
    interpolation for the zone meridian ( in this case 45 deg W) should be 
    included in calculation also.  I don't think it was included.  
    NavList message boards: www.fer3.com/arc
    Or post by email to: NavList@fer3.com
    To unsubscribe, email NavList+unsubscribe@fer3.com

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting Code:

    Custom Index

    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