Transcript

INSTRUCTOR:

As the sun sets behind Mount Teide, we're reminded that the apparent motion of the sun across the sky is actually caused by the rotation of the Earth. As the planet turns on its axis, the sun first rises in the east, comes to a highest point in the south, and then sets here in the west.

Now, after dark, of course, the Earth keeps turning. And so the moon and all of our celestial objects will follow a similar path across the sky, from the east, to a highest point in the south, and setting in the west. Looking to the north, that's the north celestial pole. And that's the one fixed point in the sky. And the entire celestial sphere appears to rotate about this point.

This is all crucial to planning your observations with Coast, because it's important to know when a particular object is going to be visible, where to find it in the night sky, and what's the best time to observe it. So for instance, if the object you're interested in is in the western part of the sky as the sun's setting, that means the object's going to be setting as well soon after dark. So you should plan to observe that one early on in the evening. Whereas if an object's in the eastern part of the sky, that means it's rising. So you can plan to observe that one later in your observing session when it's nice and high.