Gale Observatory


We are living in a Golden Age for astronomy, and Grinnell College offers its students a range of opportunities to experience the excitement of direct involvement in astronomical observation and investigation. The unusually sophisticated instrumentation at Grinnell's observatory supports activities ranging from casual visual observing to active astronomical research and allows students to do projects that are connected to topics of current interest, such as the expansion of the universe and the behavior of pulsars.

Grinnell is a liberal arts college that encourages students to explore a variety of academic areas as well as attain a high level of expertise in their major area of study. The observatory and the activities associated with it operate in a way that supports this goal: the resources are available to broaden the experience of students for whom science is a secondary interest, and the advanced instrumentation gives students who will pursue careers in physics or astronomy a chance to work with modern equipment, computers, and techniques. Because of the relatively small size of the college, the students at Grinnell work closely with faculty in classes, student projects, and research. Grinnell is unusual in offering students the resources to do work that is more sophisticated than is possible at most undergraduate institutions, while offering the close contact between faculty and students that is difficult to find at large, research-oriented universities.


If you would like to be added to the e-mail list for information about meetings of the Grinnell College Astronomy Group please email Stephanie Peterson.

For specific information about the observatory, contact:

  • Robert Cadmus, Professor of Physics
  • Grinnell College, Grinnell IA 50112
  • email:
  • phone: 641-269-3016


The primary astronomical facility at Grinnell College is the Grant O. Gale Observatory, located on the edge of the campus only a few minutes walk from the center of the campus and the dormitories (see the campus map). Because the town and the college generate relatively little light, the sky at this convenient location is dark enough to do demanding observing projects, such as spectroscopy of faint galaxies. Grinnell students can work on astronomy projects without the necessity of arranging transportation to an observatory at a dark site miles away from the lights of town.

The observatory was constructed in 1983 and houses a 24" (0.61m) Cassegrain reflecting telescope built by DFM Engineering. The telescope is completely computer-controlled. Instrumentation includes a spectrograph with both photodiode array and CCD electronic detectors, a sophisticated CCD camera system, two photoelectric photometers, and three video camera systems, two of which are equipped with image intensifiers. The observatory therefore supports all three of the major techniques used by observational astronomers: spectroscopy, imaging, and photometry.

Computers are used extensively at the observatory for both the acquisition and analysis of data. In addition to the computer system that controls the telescope, four Sun Microsystems UNIX computers are available for students' use at both the observatory and the science building. The software on these systems provides sophisticated image processing, graphics, and other data analysis capabilities.

Faculty Research

Faculty and research programs: Three of the nine regular members of the Physics Department faculty are engaged in astronomy research.

Robert Cadmus studies the pulsation of semiregular variable stars using data acquired at Grinnell's observatory.

Charlotte Christensen researches the evolution of galaxies over the history of the Universe using high-resolution computer simulations.

Charles Duke works in high-energy gamma-ray astronomy using a specialized telescope located in Arizona.

The results of Grinnell astronomy research have been published in primary journals. Students are encouraged to work with faculty on their research. Full-time research positions are available in the summers and part-time work is often available during the academic year.

Student Opportunities

Opportunities for students with a casual interest in astronomy

Open houses are held at the observatory from time to time so members of the campus community, the general public, or special groups can view celestial objects through the 24" telescope. There is no set schedule for these events, but they are announced in the local media. Arrangements for group visits can be made by contacting Robert Cadmus (641-269-3016).

A descriptive astronomy course is offered for those students who are interested in learning more about astronomy, but who are not planning to take courses in the regular physics sequence. Students in this course use the observatory both for visual observing and more instrumentation-oriented projects.

Opportunities for students with a more serious, but not professional, interest in astronomy

There are several options available to students who would like to do a modest amount of relatively sophisticated work in astronomy. Astronomy projects are available to students in some physics courses beyond the introductory level and independent study projects can be arranged for students with appropriate backgrounds. Examples of such projects are described below. These students may also be able to participate in the astronomy research programs.

Opportunities for students who are considering a career in astronomy

The resources available at Grinnell are ideal for students who intend to pursue graduate study in astronomy and ultimately become professional astronomers. Although it was not always so, today astronomy is essentially a subdiscipline of physics and a career in astronomy must be built on a strong foundation of physics. In fact, admission to graduate school in astronomy does not require a background in astronomy, but does require a strong physics background. Grinnell offers an academic program that is perfectly suited to this situation: a strong physics curriculum combined with interesting and enlightening hands-on experience in astronomy and a high quality liberal arts education. With the exception of occasional special topics courses in astronomy and astrophysics, Grinnell students who are planning on graduate study in astronomy do not take formal classes in astronomy. Instead they concentrate their course work in physics, and get valuable astronomy experience through individualized activities such as independent study projects and participation in research. This approach has been very successful and Grinnell graduates have a good record of success as astronomers. In recent years each graduating class has included students who have gone on to pursue the Ph. D. degree in astronomy.

Student Projects

The greatest strength of Grinnell's astronomy program is the opportunity it provides for students working individually or in small groups to undertake a wide range of interesting astronomical investigations. Whether a project is done in conjunction with a regular physics course, as a separately designed individual independent study course, or as an informal activity, every effort is made to strike the right balance between student independence and student-faculty collaboration.

Examples of projects that students have done include:

  • Determination of the age of the universe using galaxy redshift and distance data taken at Grinnell's observatory
  • Studies of the excitation of atoms in planetary nebulae
  • Measurement of the rotation curve of a galaxy showing the presence of "dark matter"
  • Determination of the orbit of a binary star by observation of the shifts in its spectrum
  • Measurement of the optical light curve of the Crab Pulsar
  • Measurement of the age and distance of star clusters
  • Spectroscopic investigations of the reflectivities of planetary surfaces and atmospheres
  • Investigation of the increase in the opacity of the earth's atmosphere as a result of the Mount Pinatubo volcanic eruption using stellar brightness measurements


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