Wednesday, June 6, 2018

Basic Training - Basic Celestial Navigation

Don't panic or go crazy. The celestial navigation we're going to use is only the most basic.

If you don't have a compass, knowing the cardinal directions (that's North, South, East, and West for Common Core grads) is enough for starters.

If you want to learn greater detail than that, plot the constellations, define your latitude or find noon with a sextant, ROWYBS; you'll have to take a much more in-depth course. It's beyond the scope of a class for basic training, but feel free on your own time to go deeper.

What we're concerned with, quite simply, is finding North, or South.

In the Northern Hemisphere, assuming a clear night sky and basic intelligence, you do two things.

You find Ursa Major, i.e. the "Big Dipper". (And for Brits, "The Plough".)

Then you take the two stars that form the far lip of the dipper opposite the "handle", follow them in the direction they align for about 5½ times as far as they are apart, and you come to Polaris, in Ursa Minor, aka the "Little Dipper".

From wherever you're standing in the Northern hemisphere, straight down to the horizon from that point is due north.

That's it.

Once you know North, you can figure out East, West, and South.

You can do the same thing in reverse in the Southern Hemisphere (because you can't see Polaris from there) by finding the Southern Cross.

Absent a compass or protractor and map, anything else is navigation by guess and by God, and pretty rough indeed.

Beyond that, the sun and moon both rise in the East, and both set in the West.
How far North or South of directly East and West is a function of the season, and your actual latitude on the globe.

And the moon rotates on a roughly 28+ day cycle: there is a full moon every four weeks, and a new moon (blacked out) the same span apart, 14 days later. People who don't pay attention should know that the moon starts appearing on the right side of the crescent, and fills out from right to left, then disappears in the same way. So if you didn't know before, know you know whether the moon's getting bigger ("waxing") or smaller ("waning"), and again by calibrated eyeball, you know how many days until it's full, or dark ("new").

On cloudy nights, you're S.O.L. for any of this.

For basic wayfinding though, it could be enough to get you pointed in the right direction. Or headed away from a bad one.


Anonymous said...

One of the things I most wanted to take away from my commissioned service was mariners celestial. It's really based on a falsehood; that the stars rotate around the earth. I got good at it but using a sextant is a very perishable skill.
What you have here is just right for the purpose and audience intended.
Boat Guy

Aesop said...'re saying the stars don't rotate around the earth?
The Earth isn't the center of the universe??
Pope Urban VIII is gonna be pissed...

Anonymous said...

Here's one I've found useful:

In the Northern Hemisphere, take your analog (i.e. with HANDS) watch, point the hour hand at the sun. Bisect the angle between the hour hand and the 12, that points South. Adjust your watch first if it's set to Daylight Savings Time. There's a similar method for the Southern Hemisphere, I don't have it off the top of my head and I'm too lazy to look it up.

I learned this many moons ago from, of all places, a Ripley's Believe it or Not book.

This is especially useful because, unlike finding Polaris, it can be done during the day when you're likely to be up and moving about. Of course it's a backup to a compass, but you're probably wearing a watch anyway, and no one ever died from having too many ways of figuring out which way they're travelling.

Here endeth the lesson.

Mark D

Aesop said...

Which will be covered under Survival. Because if GPS, map & compass, and Polaris aren't doing it for you, you're pretty well screwed, right?
And I'll look up South-finding for you when I get there. ;)

Anonymous said...

Being one of the few people left who is actually wearing an analog watch (you do know we're having to TEACH the "clock system" to the young'uns now, right?)that's handy, but I will likely not be up and moving around in daylight.

G-man said...

While the navigation w/o a map or compass is 'by guess or by God', if you at least remember the basics of your AO (really large features like mountains, rivers, or large roadways), you can quickly combine this 'which way is North?!?' with the handrailing technique mentioned previously. Not that our gracious host needs this explained. Thus you can quickly get toward or away from any particular section of the AO if necessary. Now if you're dropped somewhere for which the major terrain features are not tattooed on the inside of your noggin, you have an entirely different set of problems.

Anonymous said...

Learn to recognize the planet Jupiter and certain constellations like Orion and Scorpio as at least in the Northern Hemisphere they rise roughly in the east and set in the west

Somewhere Behind Enemy Lines
Peoples Republik of Kommiefornistan

RandyGC said...

Agree with Boat Guy. However if I ever run across a good sextant at a price I could afford I might refresh my skills just for S&Gs.

Once I got the hang of it it was kind of fun, the most difficult part was resolving our position from your sightings while traveling a 600 Kts at 25,000 feet on a fixed schedule.

FYI, the Long Range Desert Group used celestial to navigate in the deep desert in North Africa, which allowed them to skirt the Afrika Korps who did not patrol areas the locals told them were un-navigable due to lack of landmarks and surveyed maps.

Aesop said...

And if anyone has a line on one of those LRDG hood-mounted Bagnold sun compasses, I want three.