A Viewing Constellations from Opposite Hemispheres

[abhiask11]

When we see moon or other constellations which orbits near to equator imaginary line, they looked upside down from southern hemisphere, but if a constellation located far in South like Crux constellation, would it also look upside down from northern hemisphere?? Please advise.

 

[Drakkith]

In general it depends on your orientation and your latitude compared to the declination of the constellation. I could turn around and bend over backwards to see a constellation rotated 180 degrees, or be at 45 degrees south latitude but viewing a constellation with -75 degrees declination, in which case it would have the same orientation as it does when viewed from 20 degrees north. But it's a good rule of thumb, yes.

 

[abhiask11]

Thanks a lot for your explanation. So can I conclude with this, if both the observers from northern and southern hemisphere are facing towards South (they don't bend over) to see a constellation which is located far in South and visible to both the observers, so constellation will look similar to both of them as their orientation is same?

 

[abhiask11]

In general it depends on your orientation and your latitude compared to the declination of the constellation. I could turn around and bend over backwards to see a constellation rotated 180 degrees, or be at 45 degrees south latitude but viewing a constellation with -75 degrees declination, in which case it would have the same orientation as it does when viewed from 20 degrees north. But it's a good rule of thumb, yes.

Thanks a lot for your explanation. So can I conclude with this, if both the observers from northern and southern hemisphere are facing towards South (they don't bend over) to see a constellation which is located far in South and visible to both the observers, so constellation will look similar to both of them as their orientation is same?

 

[collinsmark]

Let's start with something a little simpler, like the constellations of the zodiac. These constellations are all near the celestial equator.

When viewed from moderate latitudes in the northern hemisphere, a person will typically face South, and look up a little bit to see whichever zodiac constellation is highest in the sky.

But when viewed in moderate latitudes in the southern hemisphere, a person will typically face North and look up a bit.

So yes, the constellation will be flipped upside down (due to the facing North vs. facing South).

But the constellation Crux is really far South. People in moderate latitudes in the northern hemisphere won't be able to see Crux ever. Similarly, people in moderate latitudes in the southern hemisphere won't be able to see the Big Dipper (part of Ursa Major). Ever.

Even people in moderate latitudes in the southern hemisphere may need to face at least a little South when viewing Crux. (People in the northern hemisphere can't see it at all -- it's below their southern horizon).

But if you're deep into the southern hemisphere, you can see Crux all year around, as it rotates around the southern celestial pole. This is similar to how people deep in the northern hemisphere can see the Big Dipper all year around, as it rotates around the northern celestial pole. Sometimes it will look upside down compared to other times, depending on how far it is rotated around the pole.

 

[Drakkith]

Thanks a lot for your explanation. So can I conclude with this, if both the observers from northern and southern hemisphere are facing towards South (they don't bend over) to see a constellation which is located far in South and visible to both the observers, so constellation will look similar to both of them as their orientation is same?

That's right! The only difference is that the person further south will have to look 'up' more than the person in the north.

 

[tech99]

In a similar way, the Sun appears to move Right to Left when viewed by someone in the Southern Hemisphere.

 

[abhiask11]

Let's start with something a little simpler, like the constellations of the zodiac. These constellations are all near the celestial equator.

When viewed from moderate latitudes in the northern hemisphere, a person will typically face South, and look up a little bit to see whichever zodiac constellation is highest in the sky.

But when viewed in moderate latitudes in the southern hemisphere, a person will typically face North and look up a bit.

So yes, the constellation will be flipped upside down (due to the facing North vs. facing South).

But the constellation Crux is really far South. People in moderate latitudes in the northern hemisphere won't be able to see Crux ever. Similarly, people in moderate latitudes in the southern hemisphere won't be able to see the Big Dipper (part of Ursa Major). Ever.

Even people in moderate latitudes in the southern hemisphere may need to face at least a little South when viewing Crux. (People in the northern hemisphere can't see it at all -- it's below their southern horizon).

But if you're deep into the southern hemisphere, you can see Crux all year around, as it rotates around the southern celestial pole. This is similar to how people deep in the northern hemisphere can see the Big Dipper all year around, as it rotates around the northern celestial pole. Sometimes it will look upside down compared to other times, depending on how far it is rotated around the pole.

Thanks. But Crux can be seen from few countries located in northern hemisphere like Hawaii and Sri Lanka. They are close to equator but above the equator towards North.

 

[Ibix]

Somewhere on Earth there's a point (probably in the ocean...) where you are directly under the center of the constellation. Get a group of friends to stand in a ring around you and then walk directly away from you. Do their "directly overhead" directions move in the same way? Is the same star nearest directly overhead for all of them?

It isn't really north versus south that controls the orientation. If you draw concentric rings around the point on Earth where the constellation is directly overhead, it's where you are on one of those rings.

 

[collinsmark]

Thanks. But Crux can be seen from few countries located in northern hemisphere like Hawaii and Sri Lanka. They are close to equator but above the equator towards North.

Yes, I was specifically referring to moderate latitudes rather than tropical latitudes.

But if you're far enough South, even in the southern hemisphere's moderate latitudes, you'll be able to see Crux every night of the year, all night long (assuming clear skies, and nothing obstructing the horizon, such as trees, mountains, buildings, and the like). Sometimes, Crux will be high in the sky, and "right-side up." And sometimes it will be low in the sky, near the southern horizon, but upside down. This is because it rotates around the southern celestial pole, and the southern pole is moderately high in the sky itself.

What's more, if you're in one of these moderate or greater, southern latitudes, you won't be able to see constellations that are near the northern celestial pole, ever (such as Ursa Minor or even the Big Dipper [part of Ursa Major]).