Skynet University courses are designed to work with most introductory astronomy textbooks. At the University of North Carolina, we use Astronomy Today by Chaisson and McMillan. Astronomy Today is currently on its 8th edition, and can be purchased here for $134 new or $36 used (as of 5/17).
However, we find that introductory astronomy textbooks do not change significantly from edition to edition, so the 7th and even 6th editions are also acceptable. The 7th edition can be purchased here for $66 new or $28 used (as of 5/17). The 6th edition can be purchased here for $31 new or $8 used (as of 5/17).
This textbook can be used for both Astronomy 101: The Solar System and Astronomy 102: Stars, Galaxies, and Cosmology.
No textbook is necessary for Astronomy with Skynet: Our Place In Space! or Astronomy with Skynet: Astrophotography.
Educators: If you use a different textbook at your institution, let us know at introastro at unc dot edu. We can likely support it too.
