NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Compass Check
From: Don Seltzer
Date: 2016 Mar 21, 19:48 -0400
On Mon, Mar 21, 2016 at 6:28 PM, Bill Lionheart <NoReply_Lionheart@fer3.com> wrote:
>
> ... Correcting a compass with the sun. Its strange that I never learnt
> this in a navigation class but it is clearly why binnacle compasses
> have a spike in the middle to cast a shadow. I have an old Sestrel
> compass with a much bigger and better spike.
'The pilots now their azimuth attend,
On which all courses, duly form'd, depend:
The compass placed to catch the rising ray,
The quadrant's shadows studious they survey;
Along the arch the gradual index slides,
While Phoebus down the vertic-circle glides;
Now seen on ocean's utmost verge to swim,
He sweeps it vibrant with his nether limb.
Thus height and polar distance are obtain'd,
Then latitude, and declination, gain'd ;
In chiliads next the analogy is sought,
And on the sinical triangle wrought:
By this magnetic variance is explored,
Just angles known, and polar truth restored.'
- William Falconer
Don Seltzer
From: Don Seltzer
Date: 2016 Mar 21, 19:48 -0400
On Mon, Mar 21, 2016 at 6:28 PM, Bill Lionheart <NoReply_Lionheart@fer3.com> wrote:
>
> ... Correcting a compass with the sun. Its strange that I never learnt
> this in a navigation class but it is clearly why binnacle compasses
> have a spike in the middle to cast a shadow. I have an old Sestrel
> compass with a much bigger and better spike.
'The pilots now their azimuth attend,
On which all courses, duly form'd, depend:
The compass placed to catch the rising ray,
The quadrant's shadows studious they survey;
Along the arch the gradual index slides,
While Phoebus down the vertic-circle glides;
Now seen on ocean's utmost verge to swim,
He sweeps it vibrant with his nether limb.
Thus height and polar distance are obtain'd,
Then latitude, and declination, gain'd ;
In chiliads next the analogy is sought,
And on the sinical triangle wrought:
By this magnetic variance is explored,
Just angles known, and polar truth restored.'
- William Falconer
Don Seltzer
