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Star hopping is a technique thatamateur astronomers often use to locateastronomical objects in thenight sky. It can be used instead of or in addition tosetting circles or go-to/push-to systems.
Manycelestial objects of interest are too faint to be visible to the unaided eye.Telescopes orbinoculars collect much more light, making faint objects visible, but have a smaller field of view, thus complicating orientation on the sky.
The field of view of binoculars is rarely more than eight degrees, while that of typical amateur telescopes may be substantially less than one degree, depending on the magnification used. Many objects are best observed using higher magnifications, which inevitably go along with narrow fields of view.
Star hopping uses brightstars as a guide to finding fainter objects. A knowledge of the relative positions of bright stars and target objects is essential. After planning the star hop with the aid of astar chart, the observer first locates one or more bright stars in afinderscope,reflex sight, or, at a low magnification, with the instrument to be used for observation. The instrument is then moved by one or more increments, possibly using areticle to identify specificangular distances, to follow identified patterns of stars in the sky, until the target object is reached.
Using a telescope equipped with a properly alignedequatorial mount, the observer may also follow theequatorial coordinate system on a star map to "hop" or "slide" along the lines ofright ascension ordeclination from a well known object to find a target. This can be assisted using setting circles.
Once an instrument is centered on the target object, higher magnifications may be used for observation.
A simple example of star hopping would be findingMessier 13, aglobular cluster in the constellationHercules, which is too faint to be seen by the unaided eye under most conditions. As shown on the star chart, M 13 lies on a line connecting the stars ζ Herculis and η Herculis. Using star hopping techniques an observer would first identify these two by the naked eye and then point an instrument (binocular or telescope) two thirds of the way up from ζ, one third down from η to see M 13. An observer using a telescope equipped with an equatorial mount would pan down from η in declination to site M 13.