Other Changes Have Been Motivated By The Constant Updating Of Astronomical knowledge And By My Attempts To Make Matters Clearer To You. In Part 1, Basic Astronomical Observations Are Presented More Concretely; Chapter 2 Simplifies Ptolemy's Cosmology; Chapter 3 Has A Revision In The Order Of The Presentation Of The Copernican Model; Chapter 4 Ties Together Newton's Ideas More Directly To Those Of Copernicus; Chapter 5 Deals With Spectra ( Discussion Of Other Stars Has Been Moved To Chapter 14); And Chapter 7 Has A Simplified And Shorter Section On Cosmology.