NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Deviation Card with GPS
From: Robert Eno
Date: 2006 Jul 24, 08:27 -0500
>
> I always liked to use an astrocompass for swinging and adjusting
> the
> steering compass and I have done it for many of my friends on
> their
> boats. It is much easier to use than a peloris and works with
> objects
> well above the horizon. It is especially easy to use with the sun
> since
> you don't have to compute the changing ZNs, the astrocompass takes
> care
> of the changing position of the object with just a very little bit
> of
> mental arithmetic.
>
> Lu Abel wrote:
>
> >George Huxtable wrote:
> >
> >
> >
> >
> >>But why not compare the compass reading with the bearing of a
> >>celestial body, particularly one that's low, near the horizon?
> On
> >>passage, point the bow, or the stern, at a low morning or
> evening Sun.
> >>Head off course for a moment, if necessary, to do it. Note the
> time
> >>and the compass reading. Later, work out the Sun azimuth at that
> >>moment, allow for variation, and check the result against your
> >>deviation card. You can keep on doing that job each day as a
> matter of
> >>routine, as the sailing-ship navigators used to do. On a clear
> night,
> >>there's a choice of low stars for doing the same thing.
> >>
> >>
> >
> >Again, a tried and true method -- if one is at sea and there is
> no haze
> >or fog and can see low-to-the horizon celestial bodies and there
> are
> >enough of them to provide a meaningful deviation table.
> Unfortunately,
> >God doesn't always cooperate...
> >
> >
> >
>
>
>
>
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From: Robert Eno
Date: 2006 Jul 24, 08:27 -0500
Gary,
An astro-compass has to kept level, otherwise all bets are off inasmuch as azimuths are concerned. This is why it is affixed with two spirit levels. I would think that lining up the shadow bar image with the mark and keeping it aligned with the mark in a boat would be frustrating as hell, if not impossible to achieve.
So my question is: how are you able to overcome this problem?
Robert
----- Original Message -----
From: "Gary J. LaPook" <glapook@pacbell.net> Date: Monday, July 24, 2006 2:24 am Subject: [NavList 889] Re: Deviation Card with GPS > Gary LaPook wrote:>
> I always liked to use an astrocompass for swinging and adjusting
> the
> steering compass and I have done it for many of my friends on
> their
> boats. It is much easier to use than a peloris and works with
> objects
> well above the horizon. It is especially easy to use with the sun
> since
> you don't have to compute the changing ZNs, the astrocompass takes
> care
> of the changing position of the object with just a very little bit
> of
> mental arithmetic.
>
> Lu Abel wrote:
>
> >George Huxtable wrote:
> >
> >
> >
> >
> >>But why not compare the compass reading with the bearing of a
> >>celestial body, particularly one that's low, near the horizon?
> On
> >>passage, point the bow, or the stern, at a low morning or
> evening Sun.
> >>Head off course for a moment, if necessary, to do it. Note the
> time
> >>and the compass reading. Later, work out the Sun azimuth at that
> >>moment, allow for variation, and check the result against your
> >>deviation card. You can keep on doing that job each day as a
> matter of
> >>routine, as the sailing-ship navigators used to do. On a clear
> night,
> >>there's a choice of low stars for doing the same thing.
> >>
> >>
> >
> >Again, a tried and true method -- if one is at sea and there is
> no haze
> >or fog and can see low-to-the horizon celestial bodies and there
> are
> >enough of them to provide a meaningful deviation table.
> Unfortunately,
> >God doesn't always cooperate...
> >
> >
> >
>
>
>
>
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
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