NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Amplitudes
From: Lu Abel
Date: 2010 Jun 4, 10:50 -0700
From: Hewitt Schlereth <hhew36@gmail.com>
To: NavList@fer3.com
Sent: Fri, June 4, 2010 8:10:40 AM
Subject: [NavList] Re: Amplitudes
This is in the FWIW category:
During the years I compensated compasses, I learned that small-boat
sailors would become aware when their compasses were 10° out of whack.
Some would catch on at 5°.
To give small-boat sailors a rough and ready way to check their
compasses, I developed a table of the sun's true bearing at dawn.
What I did was peg declinations to their dates and apply the amplitude
for that declination to produce the true bearing at sunrise on that
date.
True bearing at sunset is found by subtracting the sunrise bearing from 360°.
I know that nobody uses a compass much any more, but perhaps a few
dyed-in-the wool Luddites may find it of interest. :-)
Hewitt
On 6/3/10, Greg Rudzinski <gregrudzinski@yahoo.com> wrote:
>
>
> Jeremy,
>
> I seem to remember that you are using an NC - 2 Tamaya navigational
> calculator. If the LOP function on the NC -2 displays azimuths in degrees
> and minutes (like the NC-77) then the navigator can be tricked into
> misreading 000.55 on the display as half a degree instead of 000.92 degrees.
> I have made this mistake many times. My Palm program displays azimuths in
> degrees and tenths which I like better. This could be the source of your
> amplitude /azimuth discrepancy.
>
> GRudzinski
> ----------------------------------------------------------------
> 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
> ----------------------------------------------------------------
From: Lu Abel
Date: 2010 Jun 4, 10:50 -0700
Hewett:
I suspect there are many more small boat sailors who still use their compasses than small boat sailors who are up and underway by dawn so they can check their compass's accuracy by pointing their boat at the rising sun...
Lu Abel
I suspect there are many more small boat sailors who still use their compasses than small boat sailors who are up and underway by dawn so they can check their compass's accuracy by pointing their boat at the rising sun...
Lu Abel
From: Hewitt Schlereth <hhew36@gmail.com>
To: NavList@fer3.com
Sent: Fri, June 4, 2010 8:10:40 AM
Subject: [NavList] Re: Amplitudes
This is in the FWIW category:
During the years I compensated compasses, I learned that small-boat
sailors would become aware when their compasses were 10° out of whack.
Some would catch on at 5°.
To give small-boat sailors a rough and ready way to check their
compasses, I developed a table of the sun's true bearing at dawn.
What I did was peg declinations to their dates and apply the amplitude
for that declination to produce the true bearing at sunrise on that
date.
True bearing at sunset is found by subtracting the sunrise bearing from 360°.
I know that nobody uses a compass much any more, but perhaps a few
dyed-in-the wool Luddites may find it of interest. :-)
Hewitt
On 6/3/10, Greg Rudzinski <gregrudzinski@yahoo.com> wrote:
>
>
> Jeremy,
>
> I seem to remember that you are using an NC - 2 Tamaya navigational
> calculator. If the LOP function on the NC -2 displays azimuths in degrees
> and minutes (like the NC-77) then the navigator can be tricked into
> misreading 000.55 on the display as half a degree instead of 000.92 degrees.
> I have made this mistake many times. My Palm program displays azimuths in
> degrees and tenths which I like better. This could be the source of your
> amplitude /azimuth discrepancy.
>
> GRudzinski
> ----------------------------------------------------------------
> 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
> ----------------------------------------------------------------