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With respect to Sun shots vs full Sumner line navigation, I understand
that a poll of small boat voyagers (ie, your average offshore pleasure
boat voyager) showed that the vast majority of them did ONLY Sun shots.
Even in today's world of handheld calculators making sight reduction
so simple, my understanding is that among offshore voyagers who still
take celestial sights (vs depend solely on GPS) the majority of them
still do only Sun sights.
As we talk about position fixing, let's keep in mind the type of vessel
and where she's operating. If I'm the navigator on a high-speed
transatlantic passenger steamship that's trying to keep a schedule
year-round, I have a much greater need for constantly updated fixes than
if I'm a pleasure boat following the trade winds across the Pacific or
Atlantic at a more leisurely five or six knots. For the latter type of
folks, they're likely to be operating in much sunnier conditions and
exact position is relatively unimportant except when approaching land
(at which point I heave-to if the weather is bad enough that I can't get
good positional information).
This thread started with a discussion of the navigational log of the
Charles W. Morgan. I suspect the navigational requirements for whaler
operating in the north Pacific would be pretty much the same as the
transoceanic pleasure boat.
Lu Abel
Frank Reed wrote:
> George H, you asked:
> "If there were a few diehard old-school mariners clinging to older methods,
> then indeed position-line navigation would not have become universal. Is that
> all that he is implying?"
>
> No, nothing so wishy-washy! <g>
>
> As late as the 1930s, a substantial minority (maybe 25%??) of navigators
> were still using straight, simple time sights and Noon Sun --no celestial lines
> of position. At some earlier date, that proportion crossed the 50% "tipping
> point". I don't know when that was (and it would be very tough to prove) but
> I'm looking at 1900-1905 right now. That's sixty years after Sumner published.
> I think there are plenty of reasons for this including issues of plotting
> and charting, vessel speed, mathematical complexity, bias regarding algebraic
> versus plotted solutions, and also, perhaps, an intangible sense that a
> problem already solved did not need solved again (thou shalt not re-invent the
> wheel --and yet we do).
>
> And you wrote:
> "It seems to me that one of the conditions pushing mariners to adopt Sumner
> techniques was the climate. Mariners returning to anywhere in Northern Europe
> had to find one of the narrow approach channels around the British Isles,
> after an ocean passage. Our climate is such that the Sun may be only fleetingly
> visible for days at a time. If and when it appeared, the sextant would be
> brought out, whether it was noon or not. The chance was too precious to be
> missed. There might be weeks at a time when no noon sights were possible at all."
>
> Yes, I agree with that. Climatic differences might well explain variable
> rates of adoption of celestial lines of position in different parts of the world.
>
> By the way, somewhere in W.E. May's navigation history, there is a comment
> about pre-war navigators (meaning pre-1940s) in the merchant marine dispensing
> with position lines and "reverting to" time sights and Noon Sun. I don't
> have a copy handy, but I think I'm remembering the phrasing right. I don't think
> he's specific, but I assume he was talking about *British* navigators.
>
> -FER
> 42.0N 87.7W, or 41.4N 72.1W.
> www.HistoricalAtlas.com/lunars
>
>
