The Use of a High School Observatory to study the Metallicity Dependence of the Cepheid Period-Luminosity Relation J. Young, S. Scott, S. M. Kanbur (Physics Department, SUNY Oswego), A. Ominsky (Southern Cayuga Central School Observatory). 209 th AAS Meeting, January 2007, Seattle, WA Abstract: The Cepheid Period-Luminosity (PL) relation is one of the most fundamental relations in Astrophysics and is a crucial component in setting the size scale of the Universe and hence estimating Hubble’s constant. Recent evidence has emerged that this relation in the Large Magellanic Cloud (LMC) may be non-linear with two distinct slopes for short (P 10 days) respectively. But what of the Galactic PL relation? Here we present initial results on a project to use a high school observatory to augment existing data used to study the Galactic PL relation. Introduction: Cepheids are intrinsically variable stars which vary in brightness with periods of the order of days. The period of oscillation is thought to be linearly related to their mean absolute brightness. This relation has been thought to be linear. Recent evidence has emerged that the LMC Cepheid PL relation is non-linear and is especially non-linear at a phase of However, the Cepheid PL relation in our Galaxy, the Milky Way, is thought to be linear with current data. What is needed is more data, particularly for longer period Cepheids in the Milky Way. It is difficult to get such long periods of time on larger professional telescopes. Here we report on an effort to use a high school observatory to obtain the required data. Southern Cayuga Central School Observatory is located about 40 miles from SUNY Oswego in a “dark” part of rural upsate New York. It has a 14” GOTO Meade telescope in an observatory equiped with an internet connection and several smaller telescopes on a dark site. SUNY Oswego has purchased a ST9XE CCD camera together with a set of UBVRI filters and filter wheel to permit professional grade observations of Milky Way Cepheids. Galactic Cepheids are easily visible with such an instrument. Educational value for the local region: Figures 1 and 2 show images of the SCCS Observatory. Figures 3 and 4 are sample images taken in the lab with the CCD camera: figure 3 is a light source viewed through a 12 micron pinhole and figure 4 is a Mercury spectrum via a Fabry-Perot interferometer without filters. Further tests are underway to understand the characteristics of the CCD-telescope combination when applied to observing Milky Way Cepheids. Undergraduates from SUNY Oswego and some high school students from SCCS will be involved in this effort. These students will learn some computing, some numerical analysis and the nuts and bolts of astronomical imaging. They will also learn some astrophysics including stellar evolution and the extra- galactic distance scale by actually doing. The project will also significantly enhance the infrastructure for astronomy education in this part of New York State. Acknowledgement: Support from SUNY Oswego and SCCS is gratefully acknowledged. Figure 1: The SCCS Observatory showing the dome and telescope. Figure 2: A closer view of the 14” Meade GOTO Telescope. Figures 3 and 4: Point source image (left) and interference pattern (right) taken with the CCD camera in the lab.