Astral tracker puts us in our place

Retro project by Rice University engineering students incorporates art and science

HOUSTON – (May 5, 2017) – Call it retro-innovation. The astral tracker designed by Rice University’s Team Solar Lunar 2.0 suggests not cutting-edge breakthroughs but archaic technologies: the astrolabe, the orrery, even the sundial.

“We had a majestic object in mind,” said Team Solar Lunar 2.0 member Caz Smith. “We wanted to create an artistic exhibit that shows the real-time position of the sun and moon, connecting their locations to the location of the user. We wanted to bring people closer to the sun and moon.”

With fellow students Logan Baldridge, Liz Kacpura and Noah Kenner, Smith has designed and constructed a device as sculptural as it is astronomical. The idea came from John Mulligan, a lecturer in public humanities at Rice.

“The goal is to give you a sense of the way you relate to the celestial bodies,” Mulligan said. “You should feel yourself as a point hurtling through space. It’s an aesthetic effect I want to achieve.”

The visible portion of the astral tracker consists of two arcs attached to a vertical shaft that serves as an axis. The larger arc, painted gold, tracks the position of the sun. The smaller arc within the larger arc is painted silver and tracks the moon. An arrow on the outer rim of each arc points to the appropriate heavenly body.

Two motors are concealed in the base and two in the arcs. Using a Raspberry Pi minicomputer and the PyEphem Python Library, the tracker calculates the altitude and azimuth of the sun and moon for a given longitude, latitude and time. The calculations drive the motorized arcs to follow the azimuth of both bodies.

“We had some trouble with the electronics,” Smith said. “We’ve melted several wires, and the power supply has failed sometimes. We’re not electronics experts.” Baldridge is a sophomore and the others are freshmen. All are mechanical engineering majors. Each team member devoted roughly 10 hours a week to working on the project.

“It became an exercise in breaking down a project into its discrete parts,” Smith said. “One person did most of the wiring, one did the code and one handled the aesthetics.”

The device remains a work in progress. Electrical tinkering remains to be done. The team has prepared a 12-page instruction manual if a future team, this summer or next fall, chooses to continue the project. In the introduction to their manual the team members write:

“At the end of the semester, the device will be installed in Dr. Mulligan’s research laboratory. From there, it will ideally find a permanent home as part of a museum exhibition.”