Zum optischen Langzeitverhalten von AM Herculis I. Das Beobachtungsmaterial,die Langzeitlichtkurve und der bahninduzierte Lichtwechsel

For the variable binary AM Herculis, which is the proto-type of a subgroup of cataclysmic stars, results from the study of long-term behaviour are given. The following part of the publication concerns the observation series, the long-term light curve and the orbital light changes. On the base of 1275 photographic observations in B, V and U, most of B, covering the time interval between the years 1982 and 1991 new statements can be made about the common photometric behaviour of the star, its low and high states and the mutual correlations between them, the individual influences of the orbital light changes superimposed to the total brighhtness and last but not least about the colour behaviour of the star within these individual occurrences and the whole time interval, which is object of the second part of this study.