UW Astronomy Education Clearinghouse
"The Clearinghouse provides a way for astronomy educators to share assignments, activities, and teaching tips. This material is made available under a Creative Commons license that allows you to adapt it as you like, as long as you credit the authors and use it for non-commercial purposes. You may share your adaptation, but only under a similar license. If the original authors are unknown, please credit the "UW Astronomy Clearinghouse"