Growing up in the heat of the space race, his first exposure to the sky was taking "star trail" photos of the early Earth satellites. His interest in space migrated to an interest in astronomy in the mid-1960's. Charles made regular sunspot observations between 1967 and 1969 which formed the basis of two science fair projects, which won 2nd and 1st place in the Detroit Metropolitan Science Fair in 1968 and 1969, respectively. His interest switched to comets in 1970 when Comet Bennett, the Great Comet of 1970, made its apparition. Since then, Charles has observed nearly 250 comet apparitions visually, making photometric and other observations of these interesting objects. In 1984, he made a rare visual recovery of Periodic Comet Faye. A year later, he (along with Steve Edberg) was the first to see Periodic Comet Halley with the naked eye.

In all, Charles has published over 60 astronomical papers (1971-present), primarily on comets. Refereed papers have been published in Publications of the Astronomical Society of the Pacific, Astrophysical Journal, Astronomical Journal, Astronomy and Astrophysics, and in the books The Study of Comets (1976), and Comets (1982). Other papers/articles have appeared in The International Comet Quarterly, Sky and Telescope magazine and Astronomy magazine. Charles has been the Associate Editor of The International Comet Quarterly, a data archive/publication for comet data, since 1978. He has also published papers on satellite remote sensing of the Earth.