Find the South Celestial Pole

[Watchful]

Okay, I hope you can all find the North Celestial Pole by finding Polaris... either by way of the dippers or by using Cassiopeia, and so on. If not, let me know.

But how do you find the South Celestial Pole... you know, if you're way South of the Equator?

As you know, there's no south pole star easily visible from Earth. (You could probably see Sigma Octantis through binoculars, but it would be amid a huge mass of stars and you'd really need experience to pick it out. I put this here mostly to show off.)

Wrong way: find the Southern Cross, because it always points South!

I hear this from time to time. It's very wrong. The Southern Cross, properly Crux, points toward the South Celestial Pole (SCP): it does not always point South. It points in all directions as it wheels around the night sky.

However, if you can find Crux, you can find the SCP--and from there, you *can* find Due South.

First, find Crux. Two of the brightest stars in the sky point right to it. Crux isn't particularly huge or gigantic in the sky, so lots of folks (especially us Northy people) tend to look right past it, expecting some Orion-sized giant constellation. But the two pointers are pretty easy to find: alpha and beta Centaurus. You'll see these even in cloudy skies, and they're among the first to appear in the night sky every night. They're out year round, too!

Line them up and they point right to the top star in the cross. The cross points like a knife down to the SCP.

Hard Way: This is basically the Lofty Wiseman method. Find Crux. The SCP is four and one half times the length of Crux.

Okay, if you're like me you have no idea what that means in the field.

Watchful's Easy Way: extend your fist out to arm's length, putting the center of the pinky-side against the top star in the Cross. Three firsts down is the SCP.

The spot below the SCP (green + on my drawing) on the horizon is due South.

Here's a tip: find a stick. Break the stick so that it is as long as the width of your three fists. See the long red and green line in my sketch? Simply hold the stick up at arm's length so that the tip of the stick touches the top star in the cross, and the body of the stick lines up over the long axis of the Cross. The far end of the stick? Right on top of the SCP. Or close enough anyway to find Due South within a couple of degrees.

The stick trick is great if you're in a rocking boat: it's tough to line up your fists that way.

Also, save the stick--as Crux dips below the horizon or rotates itself around the SCP (sometimes the cross points up, my friends!), the stick trick still works. Even you move northward, and the SCP dips below the horizon or hides behind a hill, you can still find it by using the length of the stick.

PS: Pict, you might be a little too far North for this trick... Crux may be below your horizon line for a lot of the year. But if you ever can see it where you're at, or our many Oz/NZ readers, give this a shot and let me know how this works for you.!

 

[SouthernCross]

I agree.

It's always handy to know how to use the stars to determine direction.


Kind regards
Mick

 

[Watchful]

Thanks Mick!

 

[pict]

Very good post. I'm back in PA right now for a year and I'm going to miss that Southern Cross. Your description is a good one. Mac

 

[Mack]

Great info! This is the kind of thing I hang out here to learn.
Thanks.

 

[fujita yuji]

Thanks for such a useful tips. I'm just planning to visit NZ.

 

[Watchful]

Very good post. I'm back in PA right now for a year and I'm going to miss that Southern Cross. Your description is a good one. Mac

Thanks for such a useful tips. I'm just planning to visit NZ.

Again, if you guys would be willing to try that out and verify I'm right it'd be great! What works for me may not work for everyone, and I'd want to know about any adjustments that would be helpful.

And as a reminder, you may be off by a couple of degrees because some folks have larger or smaller fists than I have... but should be close enough to keep you moving in a fairly close direction.

Thanks in advance, and look forward to your future results.

 

[untamed]

Great tip Watchful! Thanks for sharing!

 

[Watchful]

Great info! This is the kind of thing I hang out here to learn.
Thanks.

Great tip Watchful! Thanks for sharing!

Thanks, everyone. I'm naturally happy to help contribute once in a while rather than just rattle cages with goofball replies and silly YouTube links... but I'm thrilled that a couple of people around the world might actually prove or disprove my claims about this method! That is SO damn cool to me!

 

[DeadeyeLefty]

Great stuff to learn, thanks man.

Can you (or anyone) suggest a good read on constellations and navigation ?
I've read some marine (celestial) nav stuff but it was pretty dry and assumed a baseline of knowledge I don't have. Thx.

 

[Watchful]

Great stuff to learn, thanks man.

VERY happy to help!

Can you (or anyone) suggest a good read on constellations and navigation ?
I've read some marine (celestial) nav stuff but it was pretty dry and assumed a baseline of knowledge I don't have. Thx.

I'll be dead honest and tell you there are two ways to go about it:

1. The hard way. This involves a byzantine mess of pointer stars, relationships, memorization, rise and set times, and so on. Should I bet that's the book on marine nav you read?

2. The damn quick way. Effectively, you need to know the following:

a. That Polaris is the North Star
b. If you see Polaris, wherever it sits above the horizon is due North. In other words, draw an imaginary line from Polaris straight down to the horizon, and that's Due North!
c. You may not see Polaris below the equator. In this case, use my method above to find Due South.

Okay.

That pretty much leaves you with needing to find Polaris.

1. The Ursa Minor method. Learn to spot the little dipper! The last star in its tail is Polaris.

2. The Ursa Major method. Problem with step one is that Ursa Minor isn't very bright, and you may not see it in light polluted areas or foggy nights. However, Ursa Major contains some pretty bright stars. Learn to spot the big dipper! The last two stars away from the tail (that form the edge of the bowl) point right to Polaris. Click on that link to see a cool animation of it.

Good news: Ursa Minor and Major are "circumpolar" stars... meaning they're up year round.

Bad news: you go far enough South, and they may not rise above the horizon... or only partially so.

3. The Cassiopeia method. Cassiopeia is a dang bright constellation of five shiny stars shaped like a W. Sometimes it's shaped like an M, sometimes like a Greek capital sigma (&#931... remember, as the hours pass, the stars spin around Polaris, so it can take on any rotation to any degree. Here it looks like an M:

Point of that is... if you look at it like a rotated W, the middle point of the triangle points right to... you got it... Polaris!

What's great about Cassiopeia is that if you go far enough South--to where Ursa Major dips below the horizon, Cassiopeia is visible! It's opposite Ursa Major. So if you lose one, you gain the other.

If you go too far South, you lose Polaris...and as I said, you go to the Crux method I started out with.

4. The Orion method. Up North, we don't always see Orion. But if you go to the Equator, where maybe you can't see Ursa Major or Minor, and maybe Crux isn't visible... and maybe you found a time of year that Cassiopeia isn't above the horizon. It is possible... but in those cases, Orion is pretty much directly obvious.

Northerners--learn to spot Orion in the Feb/Mar time frame. Big guy. Three bright stars in the belt. Actually, let's talk about that belt. If you're looking at Orion with his head up and feet down (that's the Northern Hemisphere), the three stars tilt upward from left to right. The last star in the belt is key.

When Orion rises in the Eastern sky at dusk, that star is Due East.

When Orion sets in the late evening or early morning, that star is Due West.

Not very helpful, because generally you need directions now... and most times, you don't get to see Orion when he's rising or setting. However, take note: that star moves from Due East to Due West. Always. Which means if you line it up over a tip of a tree or a radio tower, or a stick in the ground--whatever--he's pointing East to West. Plot him over about fifteen to thirty minutes, and you have a line from East to West. Draw a line 90 degrees down from the midpoint of that line and...

-- if you're in the Northern hemisphere, the line hits the horizon at due South.

-- if you're in the Southern hemisphere, the line hits the horizon at Due North.

Here's Orion from the Northern hemisphere (Southern hemisphere friends, you'll see this upside-down)

What I've given you is only a handful of easily spotted constellations. With these, you can find North, South, or East or West (ultimately) at any time of the night during any time of year from anywhere on Earth.

I can't help you use the stars if it's day, bright, or cloudy, but this is the simplest guide to celestial navigation I know. As you get more familiar with the night sky, you learn other constellations and get faster and better. But this is enough to last you.

Want to practice safely? Go online and grab some of the many great FREE astronomy programs from the web. Turn off the constellation lines, and dim the stars so you only see the first couple of magnitudes. That'll give you a light polluted sky. Play with the time/speed of the simulation, and watch how the constellations move through the sky. Bounce your location all around the earth and see how fast you can spot the important ones. If you get lost, don't panic...you're still at home on the computer!