Henry is an educational astrometry utility for performing calculations based on a Hertzsprung-Russel (H-R) diagram, such as spectroscopic parallax for working out the distance to a given star.

Unlike many other solutions that use in-built images for their H-R diagrams, Henry plots data directly from the European Space Agency's HIPPARCOS catalogue, allowing increased accuracy while also giving students greater room to experiment by exploring the catalogue themselves.

Henry runs on Windows, Mac OSX, Linux, and anywhere Qt4 and OpenGL are available. It is free (as in speech and beer) and licensed under a BSD-style license.