Micro-Lesson #8: The Ecliptic and the Celestial Equator

The topic of today's lesson is the relationship between the ecliptic and the celestial equator. This is a very basic knowledge, and it isn't really astrology but elements of astronomy; however, it needs to be digested thoroughly as it will create a firm foundation for your further studies of astrology. This knowledge will save you a lot of frustration and confusion going forward. As it is a little bit technical, I will be moving very slowly, explaining everything as clearly as I can. At any point, if you feel like you are lost, please let me know, and I'll try it again.

In the previous lesson, we discussed the ecliptic, which is the imaginary path of the Sun amongst the stars which the Sun completes in one year. It's like a big circle going around the whole of the starry sky. Understanding of the ecliptic is crucial, so if you don't have clarity about it, please re-read the previous lesson, and if something isn't clear enough there, please ask me.

Now, the equator. Of course you know what's the equator of the Earth, don't you? It's an imaginary line, or actually a circle, surrounding the Earth and separating the Northern hemisphere from the Southern hemisphere. Everything to the North of the equator is in the Northern hemisphere, like Canada and the UK. Everything to the South of it is in the Southern hemisphere, like Argentina and Australia. This is easy, right?

Let's project the equator of the Earth onto the starry sky. It will be a big circle running around the whole sky and separating it into the Northern and Southern hemispheres. That will be the celestial equator. Everything in the sky to the North of it will be in the Northern hemisphere of the sky, and everything in the sky to the South of it will be in the Southern hemisphere.

We now know two big circles running around the whole sky: the ecliptic and the equator. How do they fit together, what's their relationship? As the image below shows, they intersect. The two points formed in the intersection are very important in astronomy and astrology, they are called the points of equinoxes. One of them is the point of vernal equinox and the other one is the point of autumnal equinox.

Now, as we just said, the celestial equator splits the whole sky and everything in it into two hemispheres, so it also splits the ecliptic into two halves. One half of the ecliptic, from the vernal equinox to the autumnal equinox, goes through the Northern hemisphere, and the other half, from the autumnal equinox to the vernal equinox, goes through the Southern hemisphere. You can also see on the picture that the angle between the ecliptic and the celestial equator is approximately 23 degrees.

I think this is enough for today. There were many potentially new terms, and your homework will be to become comfortable with them. Spend some time looking at the picture, finding in it everything that was mentioned in the lesson. Better still -- print it out and hang it where you'll be able to see this picture frequently. Make a search for pictures with the keywords "ecliptic" and "equator" and see if you can find a better one, the one which will make a better illustration for this lesson. Or, if you have enough space around you, print out several different pictures of the celestial sphere, with the ecliptic, the equator and the equinoxes marked on them, and surround yourself with these pictures! The more comfortable you will be with this basic celestial machinery, the easier everything will be going forward.

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