Observation
A new comet may be discovered photographically using a wide-field telescope or visually with binoculars. However, even without access to optical equipment, it is still possible for the amateur astronomer to discover a Sun-grazing comet online by downloading images accumulated by some satellite observatories such as SOHO. SOHO's 2000th comet was discovered by Polish amateur astronomer Michał Kusiak on 26 December 2010, and the numbers are expected to continue rising steadily for the foreseeable future.
Comets visible to the naked eye are fairly infrequent, but comets that put on fine displays in amateur class telescopes (50 mm to 100 cm) occur fairly often—as often as several times a year, occasionally with more than one in the sky at the same time. Commonly available astronomical software can plot the orbits of these known comets. They are fast compared to other objects in the sky, but their movement is usually subtle in the eyepiece of a telescope. However, from night to night, they can move several degrees, which is why observers find it useful to have a sky chart such as the one in the adjoining illustration.
The type of display presented by the comet depends on its composition and how close it comes to the Sun. Because the volatility of a comet's material decreases as it gets further from the Sun, the comet becomes increasingly difficult to observe as a function of not only distance, but the progressive shrinking and eventual disappearance of its tail and the reflective elements it carries.
Comets are most interesting when their nucleus is bright and they display a long tail, which to be seen sometimes requires a large field of view best provided by small telescopes or binoculars. Therefore, large amateur instruments (apertures of 25 cm (10 in) or larger) that have fainter light grasp do not necessarily confer an advantage in terms of viewing comets. The opportunity to view spectacular comets with relatively small aperture instruments in the 8 cm (3 in) to 15 cm (6 in) range is more frequent than might be guessed from the relatively rare attention they get in the mainstream press.
Comets are assumed to orbit other stars, but they are far too small for all current methods of detecting extrasolar planets.
Read more about this topic: Comet
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