Observe meteors

Why do meteor observers venture out on cold winter nights, staring at the sky for hours? The reason lies in the small cosmic collisions between dust particles and our Earth. During certain periods, Earth passes through denser dust clouds, which mostly originate from the continuous disintegration of comets. One goal of the observations is to find out details about these particle clouds, the distribution of the particles within them, their sizes, and finally about the origin objects themselves. Since an observer group at one location on Earth can only track meteors for a few (night) hours, observers worldwide have agreed to proceed using the same methods. Which observation methods are possible? The oldest, simplest, and still successful method today is visual observation without optical aids. The observer must record both the meteors and the conditions. This particularly requires stamina and good concentration. Photographing meteors is problematic. One cannot know in advance when or where they will appear and cannot swing the camera in the direction at the moment of appearance. Therefore, a field of the sky (or with special optics the entire sky) is exposed in the hope that a sufficiently bright meteor will pass through the area. The fast movement causes only meteors from about the 0 magnitude to be captured with sensitive films and bright optics - unless one uses very costly special cameras. Additional equipment and parallel operated stations allow for the calculation of meteor paths. In light of the moving images we are accustomed to seeing of (almost) every event today, it only makes sense to think of using video cameras for meteor observation. However, even a highly sensitive commercial camcorder fails in this task. Previously, only image-intensified cameras were sensitive enough to capture meteors. Since the advent of Mintron, Watec, and similar, the situation has changed. While these cameras do not reach the brightness of an image-intensified camera, in the sensitive version (with Sony EXView HAD CCD chip) combined with a bright lens (e.g., aspherical c-mount lenses with an aperture of 0.8 by Computar), meteors can also be recorded with these cameras. Their great advantage is robustness and long life. Corresponding studies have been conducted in recent years at the Arbeitskreis Meteore - and various meteor events can thus be relived. Finally, it should be mentioned that telescopic observations show meteors up to about the 10th magnitude. A weather-independent method is radio observation. As the particles quickly enter the upper atmosphere, an ionized trail forms, reflecting radio waves. As tempting as the possibility of observation independent of weather and time of day initially seems, a meaningful processing of the vast amounts of data is problematic. Meteors can be observed every night of the year. The most important periods mentioned at the beginning of Earth's passage through meteor streams are compiled in the following table. The streams naturally have no sharp spatial limits. Therefore, the visibility duration refers to the period during which the number of meteors belonging to the stream is still sufficient for evaluation. The particles in a meteor stream move in nearly parallel paths. These paths are similar in the central part of their origin object's path. As a result of the nearly parallel paths, the meteors of a stream seem to come from an area of the sky. This location in the sky is called the radiant. The meteor streams are named after the Latin name of the constellation in which their radiant lies.

The specified maximum number of meteors per hour for an observer refers to a dark night sky without disturbing light and a zenithal position of the radiant. Under poorer conditions (haze, twilight, light from lamps and/or moon) as well as at a low radiant position, this number decreases noticeably. Meteors of a shower become visible to an observer only when the radiant is above the horizon. Most of the radiants reach a favorable position only during the night, so the best conditions are usually after midnight.

A particular branch of meteor observation is the photographic monitoring of the sky for especially bright meteors, known as fireballs. Wide-angle or fish-eye optics are usually used for this purpose. With a network of stations, there is also the prospect of determining the paths of particles entering the atmosphere. This is, as mentioned initially, an important part of AKM's activities. The European Network (EN) includes camera stations in Germany, Czech Republic, Slovakia, the Netherlands, Austria, and Belgium. Meteorite falls are rare and offer the opportunity to examine cosmic material in the laboratory. The evaluation of the photographs makes it possible to both narrow down the impact site and determine the path before the object's entry into the Earth's atmosphere. This also allows for the determination of the cosmic origin of meteorites.