New orbital elements have been measured of 359 meteors, including a large sample of Perseid and Geminid meteors. These results have been used to measure the intrinsic dispersion in the annual Perseid shower at the core of the stream. Comparison of Geminid orbits with similar data obtained in the 1950's has allowed a determination of the present annual change in orbital elements of the Geminid shower. The result is in good agreement with theoretical models of Geminid meteor stream evolution. These are but two examples of how these new orbits can be used, which serve to demonstrate the quality of the orbital data.
We want to thank all photographic observers who participated in this project as well as the visual observers who gave support by recording the times of bright meteors. Technical support was given by H. Mostert and K. Donkersloot. Many members of the Dutch Meteor Society helped over the years with reducing the negatives, notably by (in alphabetical order): H. Breukers, M. Breukers, L. Bruning, M. van Dijk, J. Nijland, J.P. van Oudheusden, M. Schuurman, G. Veldman, P. Vettenburg, M. van Vliet, K. de Voogt, and M. Wiertz. We thank A. van Genderen of Leiden Observatory and J. Eindhoven of the Technical University Twente for making available measuring facilities. We are indebted to Dr. Z. Ceplecha of Ondřejov Observatory for providing us with the FIRBAL software and for Dr. J. Tadeusz of the Astronomical Institute of the University of Poznan in Poland for the TURNER software. Proofreading of this manuscript was done by C.S. Hasselbach. P. Jenniskens is at the SETI Institute and is supported by the NASA/Planetary Astronomy program.