The mirror
was then found to preserve its position much more fixedly than
before.... At night, upon trying the telescope, we found it very
faulty for stars near the zenith, where it had been free from fault
before. The screws which we had driven hard were then loosened, and
immediately it was made very good. Then we tried with some lower
objects, and it was good, almost equally good, there. For Saturn it
was very greatly superior to what it had been before. Still it is not
satisfactory to us, and at this time a strong chain is in preparation,
to support the mirror edgeways instead of the posts that there were at
first or the iron hoop which we had on it yesterday.
Nobody would have conceived that an edgewise gripe of such a mass of
metal could derange its form in this way.
Last night was the finest night we have had as regards clouds, though
perhaps not the best for definition of objects.
THE CASTLE, PARSONSTOWN,
_1848, Sept. 2_.
I cannot learn that the fault in the mirror had been noticed before,
but I fancy that the observations had been very much confined to the
Zenith and its neighbourhood.
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