# How do you draw the ecliptic on a celestial sphere sketch?

I don't really understand how it's drawn on sketches of the celestial sphere. At first I thought it goes through east and west, but it does not. How do you know where to draw it?

Example from Roy and Clarke, Astronomy: Principles and Practice:

• When you say "celestial sphere sketch" do you mean a sketch of an actual sphere with stars drawn on the outside of the sphere? Or do you mean a sketch of the flattened map where the x axis goes from -180 to +180 and the y axis from -90 to +90? If you are sketching an actual sphere, then imagine cutting through it with a plane tilted at 23 degrees from the equator. If you are sketching the flattened map, then draw a "sine-wave"-like line that goes up and down by +/- 23 degrees.
– uhoh
Commented Jul 2, 2019 at 7:57
• An actual sphere sketch. A plane 23 degrees through the equator, but where does it intersect the horizon? At East and West? Commented Jul 2, 2019 at 11:22
• You've lost me. The plane is not through the equator, it is tilted with respect to the equator by 23 degrees, so it only intersects the sphere and and the equator at two opposite points. I don't know what "...where does it intersect the horizon?" means. The celestial sphere is just a sphere, it has nothing to do with a specific point on the Earth or a horizon.
– uhoh
Commented Jul 2, 2019 at 11:24
• Oops, I didn't double-check before adding the comment. Commented Jul 2, 2019 at 22:39
• What I meant was, where does it intersect the celestial horizon? The plane of the celestial equator (which would be ring-like in the sketch) goes through the east and west points. Commented Jul 2, 2019 at 22:42