Bruno Tilgner enquired: > As we are on the subject of unexplained pictures, please have a look > at http://aida.astroinfo.org/sposetti/Cosmos1275r.jpg. In this case > it is at least certain that the trail was produced by COSMOS 1275 r. > But what caused the sine wave pattern ? It looks as if it's a periodic error in the telescope's drive. Notice that some of the star images are elongated in the direction perpendicular to the satellite track. Further study could back out the temporal period of the oscillation and see if it corresponds to anything in the telescope's drive mechanism.