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    Re: Newbie Question - Parallel LOPs
    From: Lu Abel
    Date: 2009 Jan 29, 21:44 -0800

    Mark:
    
    I assume the times you gave were local times.  And I'm going to assume
    you are north of the equator.   What I would guess is that you made a
    mistake in your Zn calculations.   Your 1000 Zn should have been to the
    southeast and your 1400 Zn should have been to the southwest.   Don't
    know how you did your sight reductions, but if you were using the
    trigonometric equations and solving them on a calculator, remember that
    arccos (Zn)  produces two possible angles.
    
    Welcome to the list!
    
    Lu Abel
    
    Watermark wrote:
    > I've recently taught myself Celestial Navigation from library books
    > but I still have some newbie questions. I thought I was doing fairly
    > well using an artificial horizon - accuracy to within 6NM last week -
    > but today after taking sun sights at 10.00 and 14.00 all my LOPs ran
    > parallel. I reduced 8 different sights and double checked everything
    > but the same result. I had read that a 4 hour spread would be enough
    > but today my LHAs and Zn's all came out similar. My DR Long is 121W. I
    > can only deduce that taking sights of the sun at a similar altitude at
    > 10.00 and 14.00 caused the LHA to be too close despite 4 hours time
    > difference? Is this correct and will this always occur taking sights
    > at this time if not moving? Excuse the naivety but like I said I am
    > still a beginner.
    > Many thanks,
    > Mark
    >
    > >
    >
    
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