Page:The story of the comets.djvu/82

48 most successful European comet-hunter seems to have been Giacobini of Nice, who has 12 comets to his credit.

Comet-hunting is a pursuit which may well be taken up by amateurs with plenty of spare time on their hands because, if the truth must be told, it involves an immense waste of time, with results which only present themselves at long intervals. Hence the difficulty of public observatories with defined programmes taking to the work. Except for this, comet-hunting may be said to be an easy matter, given a telescope of moderate, that is, handy size (say from 4 to 6 inches of aperture); a clear horizon in the neighbourhood of the Sun either in the W. after sunset, or in the E. before sunrise; and plenty of patient, plodding perseverance on the part of the observer. An eye-piece of low power and with a large field should always be used; whilst sometimes an enthusiastic seeker after comets will provide himself with an achromatic telescope specially designed for the work and known as a "comet-seeker", but this may be regarded in general as unnecessary. A comet-seeker is nothing more than a cheap equatorial provided with an inferior object-glass and coarsely divided circles, and contrived optically to command the largest possible field in proportion to its inches of aperture. A good catalogue of nebulæ is an essential adjunct, because most comets may at a first view be easily mistaken for nebulæ, and it is only by their being possessed of movement that they can be distinguished. [See Fig. 18, Plate IV.]

Concerning the designation of comets it is expedient to say something, because there is no fixed rule, and the practice is very arbitrary and inconsistent. At its first discovery the discoverer's name is usually attached to a comet. Thus, the comet which was discovered by Morehouse on Sept. 3, 1908, was known during the whole period of its visibility as "Morehouse's Comet". On the other hand Biela's Comet