NavList:

Gary responds:
Its easy, you do it in the harbor on smooth water. It just takes a few seconds on each heading to check the deviation and move the adjusting magnets. If you experiment with your astrocompass you will find, by adjusting the leveling knobs, that small deviations from perfectly level has a negligible effect on the azimuths.

enoid@northwestel.net wrote:

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...
> >
> >  
> >
> 
> 
> 
> 

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