The Moving Stars of the Northern Hemisphere


Arizona Star Trails - Circumpolar Looking North

I present a montage of time-lapses illustrating the motion of the sky in the Northern Hemisphere. 

Any stargazer should be familiar with how the sky moves, with stars rising in the east and setting in the west.

From the northern hemisphere, when we look north we see the sky rotating counter-clockwise around the North Celestial Pole, near Polaris. As you’ll see in the video, even Polaris moves, though not much over the night. The stars that never set, but just move across the northern horizon, are the circumpolar stars.

When we look south we see the seasonal constellations, the ones that rise and set, and change over the seasons.

I shot the images for these sequences from southern Arizona, in early December 2015.

So the night starts with the summer stars setting in the west and the autumn stars dominating the sky. But then Orion and the winter stars rise and march across the sky over the night, setting before dawn, as the spring stars rise.

The south-looking movie is a dusk-to-dawn sequence. Note the Zodiacal Light in the west at right in the early evening, then reappearing in the east at left before dawn brightens the sky, and as Venus and the Moon rises.

Also note the moving bands of red and green airglow, a natural phenomenon of the upper atmosphere.

 

I posted a matching set of movies in my previous blog post, shot from the Southern Hemisphere. But here’s the link to the movie.

 

Both sets of movies were shot from nearly identical latitudes – about 31°, but 31° N for Portal, Arizona and 31° S for Coonabarabran, Australia.

As such the Celestial Poles appear at equal altitudes above the horizon. And the angles that the stars rise and set at in relation to the horizon are the same.

But the direction they move is opposite. When looking 180° away from the Pole, the seasonal stars move from left to right in the Northern Hemisphere, but from right to left in the Southern Hemisphere.

Visitors from one hemisphere to the other are bound to get turned around!

— Alan, August 25, 2016 / © 2016 Alan Dyer / AmazingSky.com

 

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