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On 10/10/2014 5:46 PM, Samuel L wrote:
> Frank- "You need to learn when you can drop digits."
>
> That's the gist of what I was/am trying to determine. So what's the
> answer? Surely there has to be one. If you know then perhaps you'll tell me?

Due diligence/self help. First Google "significant digits" and
"significant figures." Purplemath offers a tidy little explanation.

Then obtain a copy of the Nautical Almanac. It has value well beyond the
daily pages. In the explanation section section it will give you
statistics on the accuracy of the daily page entries, which are not
always spot on.

Finally apply common sense. By now you understand the system works in
tenths of a minute, and the inherent precision and accuracy of sextants
and viewers on land with an AH. On the water it may be quite another matter.

As an analogy, apply common sense to a GPS readout in degrees, minutes,
and decimal minutes to the thousandth of a minute. A minute of latitude
(or longitude at the equator) is nominally 6076.1 feet. 1/10th is 607.61
feet. 1/100th is 60.761 feet, and 1/1000th is 6.0761 feet.
Suppose your handheld civilian GPS reports its accuracy at the moment is
16 feet. Then what use does the 0.0716 feet have? None. As the next
increment is 60.761 feet the 6 ft. helps to close in on your position,
but is still slop pool when precision/accuracy is 16 feet.

> My sextant is an Astra IIIB. No idea what the magnification of the scope
> is. They should've printed/stamped it on the scope but, alas, they didn't.

The standard scope magnification is stated clearly in the Celestaire
print or online catalog as 3.5 x 40. Again, due diligence!
>
> No, I can't divide an angle with degrees, minutes and seconds in my head
> and don't want to. I want to see the process and understand what I'm
> doing. It gives me a clearer grasp and understanding of the entire
> process and particularly the method used. As said many days ago, my
> original sun sight took me 3 hours to reduce. Now I can do one in less
> than 10 minutes (the best record so far has been 5 minutes). Pretty
> good, I'd say, for a numb skull.

You will start to achieve "...a clearer grasp and understanding of the
entire process and particularly the method used" when you step back and
see the forest instead of the trees. IMHO You are getting lost in the
numbers, various methods and toys. Please, put the helix circle maker
and various plotting sheets on the back burner for the moment and
purchase a Nautical Almanac and study it. All the fancy axes, high-end
chain saws and Kevlar chaps in the world will not make you a lumberjack
if you can't tell a pine tree from an oak :-)

   

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