Caused by the numerous cities and industrial areas south of my observation site (North-Rhine Westfalia, Ruhr Area, Germany), there are rather strong air turbulences (bad seeing) near the horizon. But what is bad for astronomical photographs, however, can be very nice to demonstrate atmospheric aberration and dispersion in the star trails on photographs without tracking. The lower a star is in the sky, the more pronounced is this effect, especially at very bright stars.
In this case, Sirius had an elevation of 11° on October 23, 2011, at 3.10 hours. The sky was clear, wind was at 1-2 Bft, temperature 3°C and humidity at about 80%.
I took this photograph using a Canon EOS 350D, which was focally adapted to a Maksutov (6”, 1800mm, f 12,0). After having been adjusted and properly focused, the telescope was driven at maximum speed over the right ascension axis. This makes the star transit rapidly through the field of view causing a star track on the camera chip which records the chronological sequence of the flickering of the star.
Author: Ronald Blendeck, Germany