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    Re: Advancing LOPs for precision fixes
    From: Jeremy C
    Date: 2010 Feb 17, 07:54 -0800

    Henry is absolutely correct. The maritime academies still demand advancing or retarding the LOP's to a common time. I would be interested to see what the navies of the world and Power Squadron/ Coast Guard teach.

    The least accurate tool I use in Celnav is my pencil. With a 0.5mm lead tip on the plotting sheets I use I have an accuracy about 0.2nm. I can read my sextant to 0.1' of arc. Reduction methods should offer at least 0.1' of arc precision for navigation at sea. I therefore advance or retard all of my LOP's unless the difference is less than 0.2nm. If my computer is doing the math, it displays position to 0.1nm.

    If you are shooting a round of stars in 3-4 minutes, you are both skilled and lucky. How many bodies are you shooting? Given clouds and rain showers, and the varying lumminance of the bodies, horizon and sky at different azimuths; I take nearly the entire twilight to shoot my stars. Of course, I am often taking well over 10 individual sights, so advancing or retarding my sights 15-20 minutes is quite common. I often also have to wait for a body to appear between a break in the clouds or in the sky at all in the case of lower order stars. In any case, it is prudent to assume that you will not be able to shoot a round in a small enough time to ignore advancing or retarding the lines, even at relatively slow speeds.

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