Astronomy
Courses
Introduction to Astronomy, MIT (CC BY-NC-SA)
Introduction to Astronomy, Saylor (CC BY)
Journals
Journal of Research of NIST, U.S. Government publication (public domain)
Images
Digital Diagrams for Astronomy (CC BY)
A collection of images created or adapted by Douglas College with a grant from BCcampus Open Education for the Astronomy: OpenStax textbook. Many of the images are available in several formats, with labelled and unlabelled versions to be used for assessment purposes.
Learning Tools
Stellarium (open source): planetarium for your computer
Open Textbooks
General Astronomy, Wikibooks (CC BY-SA)