True and Magnetic North to align after 360 years.

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knotman
Posts: 117
Joined: Sat Oct 26, 2013 9:37 am

True and Magnetic North to align after 360 years.

Post by knotman » Mon Sep 02, 2019 12:22 am

https://www.theguardian.com/science/201 ... 1567166523

For all you navigators. (naviguessers as well :lol: ). Sennen

DaveWalsh
Posts: 122
Joined: Sat Oct 26, 2013 9:37 am

Re: True and Magnetic North to align after 360 years.

Post by DaveWalsh » Wed Sep 11, 2019 9:20 pm

Knotman,
I am absolutely blown away by this ZERO variation thing as of 2019.
I always knew at some level that it was a moveable feast but ..............
All my active life as a navigator, on hills at first and later at sea, 10 degrees west was a given.
There were many formulas / mnemonics used to remember how to easily remember and handle this.
My own favourite was that east was actual 90 but magnetic 100.
I read a few years ago it reduced to 3 degrees.
Now its zero !
Tonight I am reading a book called "Skerries Harbour" a short history by Christopher Fox written in 1971. I stumbled on it rummaging through a second hand bookshop ("The Last Bookshop") this afternoon.
In it is reported a Notice to Mariners by the Dublin Port and Docks Board dated 26th July 1878 in which the Lat and Long for the harbour is given, and so is the Magnetic Variation - 22' 30".
Over and out.
DWalsh

knotman
Posts: 117
Joined: Sat Oct 26, 2013 9:37 am

Re: True and Magnetic North to align after 360 years.

Post by knotman » Sun Sep 15, 2019 12:37 am

Dwalco:
this site confirms what you say about Skerries. Even 26 degrees at one stage.
https://maps.ngdc.noaa.gov/viewers/hist ... clination/

Just click on any isogonic line for an supposed accurate declination since 1590 !

Enjoy. Sennen

PS: I recall, perhaps incorrectly, that a town called Eureka in Canada once had a declination of 90 degrees at one stage :o .
Today it is a much more manageable 50 degrees :lol:. Try navigating with that!

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