Astronomical discovery . ll be a great advanceon anything that has hitherto been made, and someaccount of it will therefore no doubt be of of We may perhaps begin with a brief historicalaccount of the enterprise. Photographs of thestars were taken many years ago, but only by a fewenthusiasts, and with no serious hope of competingwith eye observations of the sky. The old wet-plate photography was, in fact, somewhat unsuitedto astronomical purposes; to photograph faintobjects a long exposure is necessary, and the wetplate may dry up before the exposure is concluded—nay, even befo
Astronomical discovery . ll be a great advanceon anything that has hitherto been made, and someaccount of it will therefore no doubt be of of We may perhaps begin with a brief historicalaccount of the enterprise. Photographs of thestars were taken many years ago, but only by a fewenthusiasts, and with no serious hope of competingwith eye observations of the sky. The old wet-plate photography was, in fact, somewhat unsuitedto astronomical purposes; to photograph faintobjects a long exposure is necessary, and the wetplate may dry up before the exposure is concluded—nay, even before it is commenced, if the observerhas to wait for passing clouds—and therefore itmay be said that the successful application ofphotography to astronomy dates from the timewhen the dry plate was invented; when it becamepossible to expose a plate in the telescope forhours, or by accumulation even for days. Thedry plate remains sensitive for a long period, andif it is desired to extend an exposure beyond the the VIL —Great of Xov. yvu, 1882. (!ro)n a lliotograpk talioi at ilic Royal Obsc>Viitory, Ca/c of Cood Hope.) ACCIDENTAL DISCOVERIES 123 limits of one night, it is quite easy to close up thetelescope and return to the operations again on ^the next fine night; and so on, if not perhapsindefinitely, at any rate so long as to transcendthe limits of human patience up to the present. But to consider our particular project. Wemay assign, perhaps, the date 1882 as that in cometofwhich it first began to take shape. In that yearthere was a magnificent bright comet, the lastreally large comet which we, in the NorthernHemisphere, have had the good fortune to of us, of course, were not born at that time,and perhaps others who were alive may neverthe-less not have seen that comet; for it kept somewhatuncomfortably early morning hours, and I can wellremember myself feeling rather more resentmentthan gratitude to the man who waked me upabout four oclock to s
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectastronomy, bookyear19
