The Role of Small Telescopes in Modern Astronomy, October 14-15, 1996, Lowell Observatory

Eclipsing Binary Research and Education at Baker Observatory

George W. Wolf
SW Missouri State University

I. The Facility - Baker Observatory

At SW Missouri State University the Department of Physics and Astronomy operates the Baker Observatory, which is located 25 miles northeast of Springfield, Missouri at a dark site. The land for the Observatory and funding to get it started were donated in 1977 by William and Retha Stone Baker. The 40-acre site is located in an agricultural area and is well protected from population encroachment and the concurrent light-pollution. A single story, three room building constructed of reinforced concrete holds two Ash domes to protect the two permanently mounted telescopes. A concrete observing pad south of the building with piers for 12 portable 8-inch telescopes is used by evening astronomy labs. Several years ago the Bakers helped with the purchase of a small farm adjoining the observatory; its farmhouse is now used as sleeping quarters for the student and faculty observers.

II. The Small Telescopes and Instrumentation

The main research telescope, mounted in a 4.3 meter diameter Ash dome, is the refurbished 0.4-m Cassegrain reflecting telescope formerly known as the #2 16-inch at Cerro Tololo, now on long-term loan to SMSU. The mirrors have been re-coated, the entire electrical system has been re-wired, and the tube and mount repainted. The f/18.75 optical system was designed for the purpose of photometry, and is still in excellent condition. An electric motor is used to move the secondary mirror for focussing purposes. The equatorial mount consists of a torque tube polar axle with an offset declination counterweight arm, and provides excellent mechanical stability.

From 1990 to 1992 an NSF equipment grant (AST-9001360) was used to upgrade the drive system of the telescope and to add a CCD guider for long exposures. Positioning and guidance of the telescope have been modernized by installation of a computer-controlled closed-loop system utilizing stepping motors and optical angle encoders for both axes of the telescope. Micro-stepping motors (from Parker-Compumotor, Inc.) are being used to allow fast and slow positioning, as well as open-loop tracking.

The main CCD camera system was purchased in June 1989, and consists of a Photometrics Ltd. PM512, grade A CCD, liquid nitrogen cooled camera head, a 4 Mbyte image buffer and video monitor system, and associated camera electronics. The 512 x 512 pixel, metachrome-coated CCD has a resolution of 0.54 arc seconds per pixel and a field size of 4.6 arc minutes on the 0.4-m telescope. It has a deep full-well (250,000 electrons) and a read noise of less than eight electrons. A twelve-hole, rotating filter wheel is positioned by a computer command to a small stepping motor and contains CCD optimized UBVRI and uvby,H-beta filters.

A second research telescope, mounted in its own 3.1 meter Ash dome, is a 0.36 meter Celestron Schmidt-Cassegrain with a retrofit Byers drive. During the past year a Photometrics Star I thermoelectrically-cooled CCD system with a Thomson scientific-grade, metachrome-coated, 384x576 pixel CCD and fully configured computer has been mated with an eye-piece box and automated UBVRI filter wheel to provide a second complete CCD photometry system on this telescope. The f/11 optics are much faster than those of the 0.4 meter and permits the imaging of 10 arcminute wide fields with a small penalty in light gathering power and stability.

III. The Research

Among the known, longer-period, double-lined spectroscopic binaries there may be many, as yet undiscovered, eclipsing systems. The discovery of eclipses and the subsequent analysis of the observed light curves in such systems would add significantly to our knowledge of stellar masses. Also, among the longer-period, double-lined spectroscopic systems already known to be eclipsing are many that have no modern light curves. For the past three years at the Baker Observatory we have been conducting a survey (1) to search for eclipses in spectroscopic systems that appear promising for one reason or another and (2) to obtain modern light curves for neglected longer-period eclipsing systems with double-line spectroscopic solutions.

We have thus far observed with the Photometrics CCD system on the 0.4 meter telescope 49 double-line spectroscopic systems, ten of which are known to have eclipses. Most of the light curves have been obtained in the B,V,R and I filter regions (or just the V,R, and I for some stars). As would be expected in such a survey, most of the systems without known eclipses have still not been found to eclipse, although some have shown variability. Since this survey is still in progress and most of the systems have only been observed at intermittent phases, no definite statements can yet be made for them. Two systems which may have been found to eclipse are HD 82780 and HD 208095.

IV. The Education

SMSU has been a member of the NASA-supported Missouri Space Grant Consortium for the past five years and receives funding for undergraduate and high school student internships for interns assisting in astronomical research. During the academic year we can generally have three of four undergraduate interns and during the summer we usually have three undergraduate and three high school interns. Since the NASA Space Grant Program emphasizes the need to involve women and minorities in the research, at least half of our interns during the past few years have been women. The NASA supported undergraduate interns, and high school interns during the summer, have been involved in all aspects of this research project. Each student has worked at the observatory obtaining data while using the CCD camera and telescope, has learned to use IRAF on the astronomy workstation at the university and has had the opportunity to reduce and analyze the data obtained. And finally, all interns have delivered talks on an aspect of their research participation at annual state-level Missouri Space Grant Consortium meetings and have written corresponding research papers, which were published in a bound volume and made available at those same state meetings.

V. Acknowledgements

This research is supported by NSF grant AST-9315061 and the interns by NASA grant NGT-40029.

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