Next message: Alexandre Eremenko: "Re: CelNav without sextant"
Bill,
Compass, as I understand, is somewhat imprecise instrument.
(The one I have permits 1/2 degree in the best case,
but i am still considering buying a better one:-)
In the "thought experiment" I propose I assume that a
compass (and THUS dead reckoning) is available.
The question is : do we have means to improve on that
(or to check our dead reckoning) by CelNav
without a sextant.
I suppose the answer is "yes".
On Tue, 2 Nov 2004, Noyce, Bill wrote:
> As another way to use rising and setting of stars -- how about
> using the compass to identify the azimuth at which some circumpolar
> stars rise and set? I suspect that could tell you your latitude
> with reasonable accuracy, even without a watch. Even if you can
> only read the compass to a couple of degrees, I think the
> uncertainty in such a latitude will depend more on the uncertainty
> of refraction at the horizon. For example, consider a star whose
> path just grazes the northern horizon -- that tells us our latitude
> without being very dependent on the azimuth measurement.
>
> With a watch, you can get latitude from the length of time a star
> far from the equator is above (or below) the horizon. Perhaps you
> could also estimate when it's directly in line with the celestial
> pole, allowing you to measure some stars whose rise or set occurs
> during the day.
> -- Bill
>
