History of astronomy and cosmology, observational astronomy, astronomy education, science outreach, science and the arts
- History of astronomy and cosmology, specializing in the medieval and early modern periods, the age of Galileo, astronomy in Italy and in Wisconsin
- Observational astronomy in educational and recreational settings, including hobby astronomy, public and park programs, and related equipment
- Astronomy education for schools from elementary to undergraduate levels, in-service teacher training and public outreach programs
- Fellow, American Academy in Rome
- Author, "Between Copernicus and Galileo"
- Co-founder, UW Space Place
- Chair, working group on the preservation of astronomical heritage, American Astronomical Society