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    Re: Having trouble
    From: John Huth
    Date: 2012 Jan 9, 10:15 +0100
    Patrick - 

    I'd say that you're in about the right place, to tell you the truth.   Conditions on the horizon can always be a big issue.   I learned on the coast of Maine (and am still learning, you never stop!) and I always had problems with fog banks on the horizon, which imposed many arc-minutes of uncertainty even under 'decent' conditions.    I finally got into the habit of guess-timating my uncertainty from factors like that, so I could judge how good my sights were.

    One day, with a well calibrated Tamaya, I had a great horizon day, beautifully clear sky, a shot taken from a porch where I knew the height, and got to within an arc-minute.   That was a blessed relief for me, after years of only so-so results.   

    As far as Captain Haddock - I haven't seen the Tintin movie yet, but as Greg pointed out, the references to navigation in Das Boot seem pretty good - what I imagine navigation in a U-boat in the North Atlantic must've been like - a few decent shots and then a lot of dead reckoning in storms, when it's difficult to gauge a position, you get blown way off course.

    John H.

    On Mon, Jan 9, 2012 at 1:56 AM, Patrick Goold <goold@vwc.edu> wrote:

    I am becoming somewhat discouraged with celestial navigation.


    Randall M. has done amazing things with his artificial horizon.  I have not been able to get similar results.  I have a good mirror horizon now, thanks to some material aid from Bill Morris, but I find it of limited utility.  I tried it during the day so that I could check it against the Davis.  After some fiddling, I did get results that matched what I was getting with the Davis.  I would note that the Davis has shades and my mirror horizon does not, which makes the latter much less pleasant to use for sun sights.  But that is no issue.  I didn't build the mirror horizon for sun sights.  The Davis does just fine for those.


    But I was looking forward to shooting Jupiter and Venus, which are wonderfully dependable this time of year.  But what I found is that Jupiter is mostly well above 60 degrees and Venus under 20.  That means Jupiter is beyond the range of the sextant and Venus is so low as to be all but impossible to find in the mirror.   Though I used an optical quality mirror, stars are somewhat splattered.  Is my sextant scope responsible for that, or the mirror or the atmosphere.  This makes accuracy impossible.


    So I started going to the ocean front.  But there I find that even when the sky is clear where I am,  the ocean horizon is always obscured by a continuous cloud bank, probably over the Gulf Stream (I am looking East).  It makes finding the horizon an iffy affair.  Is there anything to be done about that? 


    So here I am with a pretty messy set of observations.   On the plus side I am getting pretty comfortable with the mathematics.  But even that little victory turns to ashes for me when I see the new Tintin movie.  Captain Haddock appears not to need an almanac or a calculator or even to actually look at the angle indicated on the arc to be able to determine his position instantly using a sextant in a moving automobile. And with an accuracy equal to my gps.   How does he do that?


    Anyway, I've got the paper and pencil part of this down pretty well, but the physical part of actually making obsevations is still sketchy.   Are there any improvements in my equipment that would help with this problem or do I just have to keep at it until I find the knack?

    Dr. Patrick Goold
    Department of Philosophy
    Virginia Wesleyan College
    Norfolk, VA 23502
    757 455 3357

    Keeping up with the grind
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