Project history

Let me introduce myself in brief: I am aged 62, interested in astronomy for 50 years, and live in Freiburg im Breisgau, Germany. Between 1975 and 1999 I observed the planet Jupiter at the Radebeul Public Observatory near my hometown Dresden, and made 1,200 drawings of the planet.

In the late 70's and the 80's I analysed drifts of features in the Jovian atmosphere, and compiled annual reports. Positions were derived from timings of Central Meridian transits, and many results came from other observers. In the mid-80's I also became interested in historical observations of Jupiter, and collected old data in libraries of Berlin, Potsdam, and Dresden. The number of observations grew fastly. Eventually in 1989 I found it necessary to store them on a harddisk. Soon an appropriate data structure, paper sheets for entering observational records, and a simple Turbo Pascal program were created.

In 1992 Grischa Hahn, another Jupiter observer of Dresden, decided to improve the software's spartan outfit and handling. He undertook virtually all programming tasks from then on. Grischa has been making huge efforts to implement many useful features in the software. Also in 1992, the project of collecting positional data was named JUPOS (like JUpiter POSitions), and the DOS software was accordingly named PC-JUPOS. Since 2002 Grischa has been working on WinJUPOS, a "multi-planet" extension of its predecessor running under MS Windows. Maintenance of PC-JUPOS was cancelled in 2005 owing to the progress of WinJUPOS.

By now we have collected 1,610,800 positions observed since 1785. (Is there anyone who possesses notebooks of Cassini, of the 17th century, showing his original C.M. transit observations?) Most of them are dated 1879 through about 1900 and from the mid-1970's onwards. However, the vast majority relates to recent apparitions well documented by electronic observations. A large gap still spans the first half of the 20th century. Data of these years is printed in the literature, but we are not able to do any library research...

In the 1990's, the co-operation with the Jupiter Section of the British Astronomical Association became especially close. JUPOS drift charts are now used by the BAA for further analysis.

Regrettably, I had to reduce my JUPOS activities due to increasing job commitments in summer 2012. I continue updating this website but suspended measuring images. My thanks are going to Michel, Gianluigi, Marco and Robert who have resumed analyzing observations by most observers I processed in previous years.


To visit the main page of the JUPOS project, go to or