I have not been teaching since I retired in 2004. But I often dream about teaching situations. This happened two days ago; In that dream I was not able to explain the parallax phenomenon. What follows is the link to a short essay I started composing after waking up. Today I finished writing it and posted the essay at: http://pages.csam.montclair.edu/~kowalski/about_parallax.html
Is my explanation correct and accurate; I am not an astronomer. Comments will be appreciated.
Ludwik Kowalski
P.S. I did not know that the distance to the moon was accurately estimated, by the parallax method in 2nd century BC
P.P.S. Feel free to share the above link with others.