Starship Asterisk*

Scenes from Two Hemispheres

Explanation: The stars of a summer night on the left and the winter night sky on the right are the same stars. In fact, both pictures were taken in late December and have similar fields of view. The left panel shows a scene from a beach on Bruny Island off the coast of Tasmania, Australia, while the right panel features the sky over the snowy Alborz Mountains of northern Iran. But if the sky on one side still looks unfamiliar to you, just put your cursor over the image to see an alternate version. The alternate image will trace the outlines of the familiar constellation of Orion, as seen from the southern and northern hemispheres of planet Earth.

Now this is cool. Two different perspectives of the same subject… it would be nice to see more of this sort of APOD such as side by side images of the same subject in different wavelengths. There have been similar APODs using overlay. Those are cool too!

Can someone explain why the stars seem to have rotated 180 degrees, but the angle between Iran and Tasmania is probably closer to 90?

casusbelli wrote:Can someone explain why the stars seem to have rotated 180 degrees, but the angle between Iran and Tasmania is probably closer to 90?

Longitude doesn't matter here.

Iran & Tasmania are near mirror images latitudinally.

The 180 degree rotation is achieved by having one view look east
at a rising Orion & the other view look west at a setting Orion.

Thanks,
but I didn't mention longitude.
Iran and Tasmania likely are under 45 degrees north or south, so together, again, are not more than 90 degrees apart latitudinally. So still unanswered.

I don't think dusk vs. dawn matters. Orion goes across my sky with his head up at both. No rotation overnite. Am I wrong?

Having never been down-under so to speak I would have been lost finding stars and constellations Thanks for giving me the new perspective.

Now I wounder why our Aussie friends never mentioned this before

Orion isn't directly overhead. It looks as though it appears roughly 45 degrees above the horizon in both of these shots. 45 degrees + 45 degrees makes up your 90 degrees. [Actually it's a little more in both images, but I'm oversimplifying to match the question.]

Keep in mind that the 0 degree division between the northern and southern skies is very close to Orion's belt, so it will be at about the height in the sky of the latitude of the observer.

Another perspective: In the northern Hemisphere you can see the north star, while the constellation Octans, near the southern pole, is hidden below the horizon. In the southern hemisphere Octans is above the horizon while the north star is hidden. While looking at Orion from the northern hemisphere shot the north star is "up" (behind your head), while in the southern hemisphere Octans is "up" (behind your head)

-Noel

Remember it is the earth that is rotating, not the sky background. Picture yourself on a small circle about ten feet from a wall. The constellations are drawn on the wall in an upright position, they don't change. Now picture yourself on the upper half of the small ball (northern hemisphere of earth) looking at the wall (Orion) it looks from your perspective right side up. Now picture yourself upside down, below the horizon of the ball (earth) in the southern hemisphere looking at the wall. What do you see? Most of us (used to seeing the Constellations in the northern hemisphere) would see "Orion" upside down. That said, I have difficulty figuring out what you would see if you lived (and observed) at the equator?

casusbelli wrote:Thanks,
but I didn't mention longitude.
Iran and Tasmania likely are under 45 degrees north or south, so together, again, are not more than 90 degrees apart latitudinally. So still unanswered.

The APOD shows:
Orion sets in the west with the 3 belt stars running horizontally in Iran.
Orion rises in the east (upside down) with the 3 belt stars running horizontally in Tasmania.

Not shown:
Orion rises in the east with the 3 belt stars running vertically in Iran.
Orion sets in the west (upside down) with the 3 belt stars running vertically in Tasmania.

90º is due to latitudinal difference.
90º is due to looking east vs. west.

For reference, the images were taken at about 37 degrees north and about 42 degrees south.

-Noel

Wow, so you people in the northern hemisphere see everything upside down! Weird, how do you cope?

Cheers -

Rob (Australia)

Rob_K wrote:
Wow, so you people in the northern hemisphere see everything upside down!
Weird, how do you cope?

http://www.youtube.com/watch?v=FuA8K1mQWMc

I live in central Arctic of Canada but am confused what happens at the equator. Is Orion visible? And if so, which part?

DougStern wrote:I live in central Arctic of Canada but am confused what happens at the equator. Is Orion visible? And if so, which part?

From 80ºN Orion can currently be seen in its entirety due South at around 9:45PM .

http://www.fourmilab.ch/cgi-bin/Yoursky

From 80ºS Orion can currently be seen (upside down) in its entirety due North at around 9:45PM;
however, it is also the land of the midnight sun down there.

DougStern wrote:I am confused what happens at the equator. Is Orion visible? And if so, which part?

At this time of the year near the equator, Orion becomes visible in the East after sunset around 20.00 hours, then climbs straight up with Betelgeuse near Zenith around midnight, and comes close to the western horizon around 04.00 in the morning.

Case wrote:

DougStern wrote:I am confused what happens at the equator. Is Orion visible? And if so, which part?

At this time of the year near the equator, Orion becomes visible in the East after sunset around 20.00 hours, then climbs straight up with Betelgeuse near Zenith around midnight, and comes close to the western horizon around 04.00 in the morning.

Oops...I misread DougStern.

Yes, Orion rises on his back and sets (180º rotated) on his stomach.

Where ever Orion is seen rising there is always an equivalent parallel in
the opposite hemisphere where Orion can be seen setting but rotated by 180º
(although it may still be daylight in the southern hemisphere).

Rob_K wrote:Wow, so you people in the northern hemisphere see everything upside down! Weird, how do you cope?

Cheers -

Rob (Australia)

No no!

You all see it wrong. You also drive on the wrong side of the road as well. Do you shake with the left hand or right?