Discovery of Helium in the Sun: Spectroscopy, Coronium, Nebulium, and the Periodic Table
By: 
Paul A. Heckert
Percival Lowell and Martian Canals: Lowell's Speculations about Water and Life on Mars
By: Paul A. Heckert
Jansky's Early Radio Astronomy: At Bell Labs Karl Jansky Discovered Celestial Short-Wave Signals
By: Paul A. Heckert
Ptolemaic Geocentric Astronomy: Ptolemy's Geometric Devices Deferent, Epicycle, Eccentric, & Equant
By: Paul A. Heckert
Ptolemy, Astronomy, & Almagest: The Ancient Greek Ptolemaic Geocentric Astronomical System
By: Paul A. Heckert
