Telescopes and recording systems used by amateurs for studying planets in our solar system - an overview

Kurzfassung

<p>During the last couple of years, engaged amateur astronomers have benefited by the rapid development in the field of commercial CCD cameras, video techniques, and the availability of mirror telescopes with high quality. Until recently, such technical equipment and the related handling experience had been reserved to research institutes.</p><p> This contribution presents the potential capabilities of amateur astronomers and describes the approach to the production of data. The quality of the used telescopes is described with respect to aperture and resolving power; as well as the quantum efficiency of the used sensitive b/w CCD cameras with respect to the detectable wavelength.</p><p> Beyond these facts the necessary exposure times for CCD images using special filters are discussed. Today's amateur astronomers are able to image the bodies of the solar system in the wavelength range between 340 and 1050 nm. This covers a wide range of the spectrum which is investigated with cameras on board of space telescopes or planetary probes.</p><p> While space probes usually obtain high-resolution images of individual Surface or atmospheric features of the planets, the images of amateur astronomers show the entire surface of the observed planet. Both datasets together permit a more comprehensive analysis of the data aquired in each case. The “Venus Amateur Observing Project” of the European Space Agency is a first step into a successful co-operation between amateur astronomers and planetary scientists.</p><p> Individual CCD images captured through the turbulent atmosphere of the Earth usually show characteristic distortions of the arriving wave fronts. If one captures hundreds or thousands of images on a video stream in very short time, there will be always also undistorted images within the data. Computer programmes are available to identify and retrieve these undistorted images and store them for further processing. This method is called "Lucky Imaging" and it allows to achieve nearly the theoretical limit of telescopic resolution. By stacking the undistorted images, the signal-to-noise ratio of the data can be increased significantly. "Lucky Imaging" has become a standard in the amateur community since several years.</p><p> Contrary to space based observations the data rate is not limited by the capacity of any radio transmission, but only limited by the scanning rate and capacity of a modern computer hard disk. An individual video with the uncompreesed raw data can be as large as 4 to 5 GB.</p><p> In addition to the video data, so-called meta data such as the observing location, the recording time, the used filter, environmental conditions (air temperature, wind velocity, air humidity and Seeing) are also documented. From these meta data, the central meridian (CM) of the observed planet during the time of image acqusition can be determined. After data reduction the resulting images can be used to produce map projections or position measurements of albedo structures on the planetary surface or of details within atmospheric features.</p><p> Amateur astronomers can observe objects in the solar system for large continuous time periods due to the large number of the existing observers e. g. the members of the Association of Lunar &amp; Planetary Observers and their telescopes. They can and react very fast to special events, since they do not have to submit requests for telescope time to a national or international organization.</p>