Free the Textbook

Astronomy Open Textbook Resources 

• Astropedia is an astronomy learning tool and intended either as a supplement for classroom instruction. 
• Khan Academy Astronomy Resources
• LibreText Astronomy Resources
• OER Commons: Astronomy is a collection of 1045 courses and resources for teaching Astronomy.
• OpenStax Astronomy is designed for one- or two-semester introductory astronomy courses.
• Teach Astronomy