On Sun, 27 Nov 2016 10:09:46 -0800, Jeff Liebermann wrote:
You're unlikely to have a working Android device available in an
emergency.
You're right Jeff, but one nice thing about knowledge is that you have
*that* always with you, even in an emergency.
So, one goal, always, is to *learn* how to do celestial navigation, where,
in a pinch, you can approximate given the experience gained using the
battery operated tools.
At best, a WWV/WWVB receiver, reasonable accurate clock,
and HO229 sight reduction tables or this years nautical almanac.
Really on the accurate clock? C'mon. I'll bet a five-dollar digital watch
has better accuracy than all the navigators had in the age of exploration.
If
you're going to impress a math teacher, then *YOU* get to do the
required math, not the computah.
Yes. Indeed. But I would like the help of the instruments and the
calculations, since, half of math is just intuition on how to do it (which
is gained by being right before, when you have more tools available).
The only thing the computah does is
replace the tables and save you from the pain of interpolation.
Fine with me.
You
still have to do 3 other sextant sight corrections (index error, dip,
altitude correction).
Can a plastic protractor substitute for a sextant for our purposes?
(i.e., it's more the process than the accuracy that I'm after.)
You can download HO229 or the nautical almanac from:
http://thenauticalalmanac.com
Egads. 250 pages. For 2016 only! Another 250 pages for 2017.
Plus 180 Megabytes of celestial stuff.
Wow. There's a *lot* of learning that needs to be accomplished.
I thought it was just a sighting of about 60 stars!
There are plenty of instructional videos on YouTube under "how to use
a sextant" and such. Most deal with a noon sight, which is where you
start.
Ah, Jeff. Thanks for letting me know where you sight. Seems to me a "noon
sighting" is easy. stick a twig in the ground, mark when the shadow switches
from west to east, and bingo. That's noon at your longitude when compared
with GMT, and, voila!
I guess a noon longitude is as simple, using a rough estimate of the angle
from the horizon to the sun. Bingo. Latitude.
Since you're likely to be doing this on land, instead of at
sea, you'll need an artificial horizon for your sextant.
http://www.davisnet.com/product/artificial-horizon/
Interesting. A $32 artificial horizon. Who knew that's needed?
Seems to me a bubble meter should work as well. Right?
Can't the phone bubble meter work for an artificial horizon?
Anyway, you are correct these are land sightings.
In mountains. Santa Cruz mountains.
The rest is RTFM, arithmetic, and practice. Once you've mastered the
noon sight, try using the moon or stars. If you want a lesson in
reality, find a suitable sailboat, wrap one arm around the mast, and
then try taking a series of noon sights.
Thanks for the suggestion of starting with a noon sight, and then a moon
sight (must be a sailor's rhyme there somewhere). And yes, I get seasick,
so, I'm intimately familiar with the reality of the motion of the ocean (I
give Captain William Bligh a lot of credit for what he done did).
a. What freeware is the best one to try out first?
The free Nautical Almanac. It's in PDF form so you can display it on
a laptop, eBook reader, or whatever while you do the math by hand.
Very interesting that this PDF is all that is needed (along with a sextant
and an artificial horizon, both of which should be phone tools if you ask
me).
2017:
https://thenauticalalmanac.com/2017%...%20Almanac.pdf
2016:
https://thenauticalalmanac.com/2016%...%20Almanac.pdf
b. What are the minimum required features of that freeware
Ummm... that it's free? If you want to learn navigation, you're going
to need to learn about celestial mechanics, navigational conventions,
a fair number of new terms, and what happens when you're in a
different part of the planet.
For now, Jeff, I'm gonna be at around 35 to 40 degrees North and about 120
to 122 degrees West. After I get good at that, I can work on the other
angles.
You could learn those from a computah
program that offers a tutorial, but I believe these are best learned
with paper and pen. Once you're proficient with the process, then you
can use the computer to allegedly save you some time.
Thanks for the advice. What would be nice is learning how to do dead
reckoning with the phone as the artificial horizon and sextant and a few
well-known start (e.g., Polaris) as the frame of reference.