Leicester,
August 19th, 1880.
My Dear Sir,—As the 11-1/4 in. speculum has now been in constant use for two years, I may be allowed to express my opinion, with all due deliberation, as to its performance. It has been tried upon almost every conceivable object during that period with uniformly good results. Having also a 5 in. achromatic of the finest quality, I have been enabled to make a great number of comparisons between the two instruments, mounted side by side: and for fine definition, smallness of star discs, and freedom from chromatism, the reflector always came out victorious. Upon first mag. stars, nothing could surpass the purity of the image in the reflector; but on immediately turning to the achromatic, the outstanding violet rays were painfully obtrusive. For red stars, which are generally small, the reflector seems especially adapted. I used to be rather sceptical about the tints of red stars, but must confess, after seeing the magnificent tints of scarlet and crimson which are shown by a large aperture, that my doubts have vanished. Definition upon the planets, in good air, is simply perfect. The detail on Jupiter and Saturn reminds one of an exquisite engraving. The far distant Neptune is perfectly defined as a tiny disc, and his moon steadily visible with the 11-1/4 in. The faculæ and other Solar detail are brought out with wonderful distinctness. As for the Moon, the crispness of definition, absence of colour, and immense number of minute objects shown by the reflector, leave nothing to be desired. The gorgeous views of clusters and nebulæ: the brilliantly crowded fields in the galaxy: and the endless variety of star colours and groups are almost beyond description, and must be seen to be appreciated. I could fill pages about objects seen with the 11-1/4 in. mirror, but will not occupy more space, save to thank you for having placed such perfect instruments within the reach of amateurs.
Yours faithfully,
(Signed.)
Mr. G. Calver.
From W. S. Franks, Esq., F.R.A.S.
Leicester,
September, 1878.