Closely adjoining the walls between which the great tube
swings, is a little building called "The Observatory." In this the
smaller instruments are contained, and there are kept the books which
are necessary for reference. The observatory also offers shelter to
the observers, and provides the bright fire and the cup of warm tea,
which are so acceptable in the occasional intervals of a night's
observation passed on the top of the walls with no canopy but the
winter sky.
Almost the first point which would strike the visitor to Lord Rosse's
telescope is that the instrument at which he is looking is not only
enormously greater than anything of the kind that he has ever seen
before, but also that it is something of a totally different nature.
In an ordinary telescope he is accustomed to find a tube with lenses
of glass at either end, while the large telescopes that we see in our
observatories are also in general constructed on the same principle.
At one end there is the object-glass, and at the other end the
eye-piece, and of course it is obvious that with an instrument of
this construction it is to the lower end of the tube that the eye of
the observer must be placed when the telescope is pointed to the
skies. But in Lord Rosse's telescope you would look in vain for
these glasses, and it is not at the lower end of the instrument that
you are to take your station when you are going to make your
observations.
Pages:
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307