[2] The observer had used an 8-1/2″ reflector, however, for some years.
(_Another Letter from the same Gentleman._)
DEAR SIR,—As to the adjustments of the 8-1/2 in., I have had very little trouble, and I have tried it again on a few objects, a few nights ago, and with a 7 in. stop, and a power of 300, I split Zeta Cancri and the close double _sf_ Castor; with the full aperture they were very easy. I have also split Gamma Andromedæ with 7 in. stop, and on a very fine night. I believe 6-1/2 in. would do it.
I just got a look, on November 7th, at the shadow of Titan, on Saturn’s disc; but was driven inside before I could observe the time of its passing the centre. I have seen the Moon on two occasions with the finest definition I ever saw. Altogether I am highly pleased and proud of my telescope. I have not yet tried many faint objects; still I saw the Crab nebula in Taurus much nearer Lord Rosse’s drawings than Herschel’s, as given by Chambers.
I am, dear Sir, Yours truly, (_Signed_.) Mr. G. CALVER.
DEAR SIR,—I am perfectly satisfied with the mirror, a 6-1/2 in., now that I have tried it with _your_ flat, and I have no difficulty in seeing star disks when the air is good.
I am, dear Sir, Yours truly, (_Signed_.) Mr. G. CALVER.
DEAR SIR,—I write to tell you that I was very much pleased indeed with last night’s observations with your 18″. The star disks were good and well condensed, and stray light well gathered in, and when a good night comes I have no doubt of it.
The markings on Mars were well defined. I find the advantage of a large aperture shows itself. I have no doubt I picked up the outer Satellite, but cannot be certain till to-night, if I am permitted to see it. The only objection I have is its short focus, as it seriously complicates my labours in matching the secondary convexes for the Cassegrain form—if you can help me in the matter of a longer focus; if not I am satisfied and thankful, and must only proceed to the testing process inch by inch.
CARLISLE TERRACE, MALAHIDE, _November 6th, 1877_.
MY DEAR SIR,—I had intended to write to you before, but, from various duties, I have been obliged to postpone it from day to day. I have been working steadily, however, with your 18″, and I like it the more I use it. The figure is wonderfully perfect, and the definition of planetary details and markings most admirable.