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: a question of time or times
    From: Lu Abel
    Date: 2011 May 29, 17:28 -0700
    Yeah, it's kind of strange that the assumption is that the Navigator on an offshore voyage will use "local" time (constantly adjusted, of course, as the ship makes easting or westing) rather than simply keeping his chronometer set to GMT.   I assume these are customs derived from naval tradition, similar to the one of reporting ship's position to the captain at 0800, 1200, and 2000.  Why 4 hours before noon but eight hours afterwards?   Why exactly 1200 rather than 1300, after the navigator has had time to reduce a meridian transit sight, giving both an excellent latitude and a longitude from an advanced morning sun line?

    I've just finished teaching the Power Squadron's Junior Navigation (basic celestial) class.  They could be a little clearer, but the implication is clearly that at sea ship's clock time is purely based on longitude, while when on shore ZD is based on civil time including any change required due to daylight time.   One, in fact, does not have to look to daylight time to see an example of civil ZD not agreeing with "sea time"   US time zones stretch considerably farther west than their correct zonal boundaries -- for example, the US's Eastern time zone (ZD +5 "standard" time) extends to approximately Lo 87 W and its Central time zone (ZD +6) past the central meridian of ZD +7,  Lo 105 W!

    Lu


    From: Gary LaPook <glapook@pacbell.net>
    To: NavList@fer3.com
    Sent: Sun, May 29, 2011 3:20:59 PM
    Subject: [NavList] Re: a question of time or times

    You can set your clocks anyway you want off shore and don't have to keep zone time, just set the clocks to noon when you take the noon sight for latitude. You only have to go onto zone time (and date) when you touch shore and you want your schedule to be in sync with those ashore.

    gl
    ----------------------------------------------------------------
    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