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    Re: Cel nav in space
    From: Bill B
    Date: 2005 Jan 4, 15:30 -0500

    > Of course, there's nothing much to this navigation really. It's more or less
    > "point and shoot". ;->
    Easy for you to say.  Hockey great, Wayne Gretzky said something to the
    effect of, "It's not so important to know where the puck is, but rather
    knowing where the puck will be."
    If I take out my magic rifle with a constant projectile speed of 1000
    ft/sec, put the perceived Moon in my crosshairs (and adjust for refraction
    and the fact that it takes over a second for light from the Moon to reach my
    eye, and make a few other corrections supplied by a physics friend) and
    fire; by the time (13+ days) my projectile reaches where the moon was it
    will be long gone.  So the trick is do time/distance calculations and fire
    13+ days at the spot I calculate the Moon will be when my projectile reaches
    that spot.
    Point and shoot at a star 100 light years away?  That has to be the great
    circle route.   Where I perceive it to be is where it was 100 light years
    ago.  So I need to determine where it is now and where it will be in the
    time it takes the projectile to bridge the gap.  At least at the
    100-light-year distance it should be swirling around in the galactic center
    of the Milky Way, a break as I see it.
    It seems more complex if the craft is traveling to another galaxy also
    orbiting its galactic center.  All I know for sure is that I'm calling
    shotgun now--you drive ;-)

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