Find and adopt an OER for your instruction
Back in 2012, when the first OpenStax astronomy textbook became available, I adopted the book for my “astronomy 101” high school course. Since then, the book has been updated annually and my course is now an IB Astronomy course.
Fraknoi, Morrison, and Wolf, the authors of the book, are well-known astronomy educators and have put considerable effort into making the content up-to-date. All images are in the public domain and all the links to content, including simulations and web-based software, are free and open to use for teachers and students. The book is released under a Creative Commons license (CC BY 4.0). Instructors can share and redistribute content as long as attribution is provided.
OpenStax textbooks are available online as web content, as a downloadable app, as a downloadable PDF, or as an inexpensive print copy.
The “astro 101” pedagogy is well-established and this text follows the model very well. I use that same model in my astronomy course so the text is an excellent resource for me as a teacher.
The OpenStax University Physics textbook is less useful in my daily teaching although I use it as a secondary resource on occasion.
Create an OER for your instruction (using either low-tech, medium-tech, or high-tech tools of your choice)
I have created a wide variety of OER content, but my TeachEngineering.org lessons and labs to use with OpenStax astronomy are available via the OER Commons site. I always use the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. That includes things I create for my students or for other educators.
I also maintain a curriculum resource guide for teaching high school astronomy.