NavList:

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

Message:αβγ
Message:abc
 Add Images & Files Posting Code: Name: Email:
Re: lat/long from meridian passage
From: Gary LaPook
Date: 2011 Jan 23, 22:45 -0800
Since I have made cuch a complete mess of it I will show the whole thing as it should have been.

---------------------------------------------------------------------------------------

USING THE EQUATION OF TIME FOR CALCULATING TIME OF LAN

The NA gives it to the second. It is added or subtracted to 12:00 to find the time of Local Apparent Noon. So you do not add it to the time of meridian passage as it has already been added to 12:00 to derive the time of meridian passage. The NA gives the time of meridian passage at the Greenwich Meridian rounded to the whole minute only but the actual time of passage of the Greenwich Meridian was 12:11:29 on January 22nd.

gl

------------------------------------------------------------------------------------------------------------------------

--- On Sun, 1/23/11, Gary LaPook <glapook@pacbell.net> wrote:

From: Gary LaPook <glapook@pacbell.net>
Subject: [NavList] Re: lat/long from meridian passage
To: NavList@fer3.com
Date: Sunday, January 23, 2011, 9:02 PM

I did it again!

Obviously 12:16:29 EST is 17:16:56 Z not :29!

Should be:

Obviously 12:16:56 EST is 17:16:56 Z not :29!

gl

--- On Sun, 1/23/11, Gary LaPook <glapook@pacbell.net> wrote:

From: Gary LaPook <glapook@pacbell.net>
Subject: [NavList] Re: lat/long from meridian passage
To: NavList@fer3.com
Date: Sunday, January 23, 2011, 8:55 PM

Well this is embarrassing, I should have proofread my message!

I wrote:
" so your noon would have been 12:16:56 EST, 17:16:29 Z. "

------------------------------------------------------

Obviously 12:16:29 EST is 17:16:56 Z not :29!So the time of his noon should have been 3 seconds later to account for the change in the equation of time making it 17:16:59 Z, not the 17:16:32 Z I had written.

Another way to calculate the time of local noon is to find the time when the GHA of the sun equals you longitude, in this case 76° 21.7' west. At 1700 Z the sun's GHA was 72° 36.8' which subtracted from the longitude leaves a difference of 4° 14.9'. We then look in the increments table in the NA to find out how long it takes for the sun's GHA to change by this amount and we find that it is between 16 minutes and 59 seconds and 17 minutes. We then add this extra time to 1700 Z to find the time on the meridian of 17:16:59.5, not surprisingly, the same result as when doing the computation using the equation of time.

gl

--- On Sun, 1/23/11, Gary LaPook <glapook@pacbell.net> wrote:

From: Gary LaPook <glapook@pacbell.net>
Subject: [NavList] Re: lat/long from meridian passage
To: NavList@fer3.com
Date: Sunday, January 23, 2011, 4:41 PM

Browse Files

Drop Files

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)