The Astronomical Research Institute of the Hungarian Academy of Sciences commemorated the 100th anniversary of the birth of László Detre on 19th April, 2006. On the cosmic scale one hundred years is but a blink of an eye, but in the life of a research institute in Central Europe it is a very long time indeed, and the mere fact of its continued existence is, in itself, no mean achievement. In this context, existence does not not only mean having a pleasant building standing in a park in a pleasant area in the Buda Hills on a road named after its founder, behind a fence, displaying, for all to see, a board showing that this is indeed the Astronomical Research Institute of the Hungarian Academy of Sciences, but also that the creation of its founder is still an internationally acknowledged scientific workshop, producing work well up to the prevailing international standards. In Central Europe this cannot be taken for granted in our century. During this time the country (and within it the Institute - better known as the Konkoly Observatory) has managed to survive two World Wars, two revolutions, one world-wide economic crisis (and quite a few smaller ones), five changes of the political regime, and many smaller mishaps, not to be listed here.
As a scientist and the director of the institute, László Detre played a decisive role in the fact that our institute, despite all of the mishaps of the history in Central Europe, is respected worldwide. He was the most prominent representative of Hungarian astronomy in the 20th century. He got his PhD degree in Berlin (1929), having there such outstanding professors as Albert Einstein and Max Planck. Returning to Hungary he got a position at the Konkoly Observatory, Budapest, where he was active until his death in 1974.
He recognized that a small country, like Hungary, could carry out internationally high level research in the field of time-dependent astrophysical processes. Following his initiative, the mountain station at Piszkéstetö was established and he passed away in 1974, just before the completion of the 1 m RCC telescope, the largest astronomical telescope in Hungary so far. There are no branches in the recent astronomical research in Hungary which do not go back to his organizational work.
Since László Detre played a significant role in the whole astronomical research in Hungary, the appropriate celebration of his centenary was a scientific colloquium giving a comprehensive overview of his scientific activity and its effect lasting until now. As he was member of the Hungarian Academy of Sciences we organized this colloquium under its auspices.
Although László Detre's scientific activity and achievements are well known abroad, he remained faithful to his country all the time and he did not leave it even in the hardest times. For him, his Hungarian nationality was very important and he emphasized it many times.
Taking into account all these circumstances, our Academy hosted a memorial colloquium on the significance of the work of László Detre on April 20, 2006. All the speakers knew him personally and remember him as a person who played a decisive role in their scientific career. A significant aim of the colloquium was to present a comprehensive overview also for young people who had no opportunity to know him personally.
This dedicated issue of the Communications from the Konkoly Observatory contains the talks presented at the memorial colloquium. We are thankful to our Academy for hosting the colloquium and to the speakers for their valuable contributions.