DEAR SIR,—I am able to report satisfactorily on the mirror. On
Saturday night last I divided μ^2 Boötis, power 300, with the
8-1/2″.
Yours truly,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From the same Gentleman._
THE GODDARDS, MOULTON, SPALDING,
_January 18th, 1879_.
DEAR SIR,—I have been waiting for opportunities for testing
observations, but there have been few nights when the weather and
leisure time have concurred in giving me a chance. However, I can
say this much, that in lunar work I have had much pleasure from the
excellent definition given by the 8-1/2 in. I had some fine views of
Copernicus under high powers not long since, and am anxiously
awaiting opportunities for closer study of a particular region.
Yours truly,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From_ FRANK C. DENNETT, Esq.
10, TERMINUS TERRACE, SOUTHAMPTON,
_December 10th, 1878_.
DEAR SIR,—The 5-1/4 in. is beautiful. Last night there was a slight
frosty fog, and the air was very very steady, in fact I only
remember about one such night since November, 1875. Saturn was sharp
and hard, and the shadow of the ring intensely black, with all
powers from 168 to 372, and even with 550, obtained by removing the
field lens of 372. The very broad polar caps presented a bluish
grey, rendered more visible by contrast with a fine penumbral line
of a very slightly brownish grey close to the south border of the
ring, and which seemed to be diffused on the south border (_i.e._,
the line was diffused). I should fancy the line here referred to was
less than 1″ of arc broad; considerably less!
Turning from Saturn, I looked at ε Arietis, the present distance of
which is only 1″·17; with all powers, from 213 upwards, the
components were visible as two tiny points of light thoroughly
divorced, and with 288 power, reminding one of ε^2 Lyræ, as seen
with 120 on a 2-3/4 in. achr., only the discs seemed freer from
rings.
Later in the evening, when the definition was more fluttery, η
Orionis shared the same fate as ε Arietis, being well separated with
the same powers. The present distance of this star is only 1″·12.
Recently I divided this star with a 4-1/2 in. stop on the mirror,
power 288. I have seen ε Arietis well with the same stop too. I
think I have told you before that the 5-1/4 in., with 372 power, was
successful in dividing ε Equulei, whose distance is only 0″·97. This
is the closest star I have yet divided.
The Moon is fine too! Last night I caught a large ring close to the
terminator, near the south pole (for the Moon was only about 2-1/2
hours past full), which was looked at over the northern wall; the
view was beautiful, such gradations of light and shade, interspersed
with greys of different hues, which render the object scarcely
describable. The finest clefts and tiniest craterlets are rendered
visible. It is a puzzle to me how anyone in the possession of £16 or
£17 can go buying a refractor of from 2-1/2 to 3-1/4 in. aperture in
preference to a silvered mirror. It must be from sheer ignorance of
the beautiful views given by the latter, which is superior in every
way.
I do not think there is any other point on which I need touch now,
so I must beg to remain,
Dear Sir,
Yours very truly,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From_ THE REV. JEVON J. MUSCHAMP PERRY, M.A., F.R.A.S.
ST. PAUL’S VICARAGE, ALNWICK,
_December 20th, 1879_.
MY DEAR SIR,—I was very much interested in reading your account of
the grinding and polishing of the 37″ speculum, in this week’s E.
M., copied from the “Monthly Notices” of the R. A. S. Had I only the
wealth of my neighbours, I would give you an order for the largest
telescope you could construct. Every really good night gives me some
fresh proof of the great excellence of the 6-1/2 in. For instance,
on December 15th, I clearly and steadily saw _Enceladus_. I could
not, of course, have recognized it had it not been that this month’s
“Observatory” gave diagrams of the positions of the five inner sats.
of Saturn, for 8 p.m. on every day of this month, and a careful
search for Encel. was fully rewarded by a clear and steady view of
it at that time in its proper place. On this feat the Rev. T. W.
WEBB warmly congratulated me, and said that he had seen Encel. with
his 9-1/3″ “With,” but only when Saturn was hidden behind a bar. I
saw it clearly in exactly its proper position _without_ hiding the
planet—power 400. I have also had several good views of Mr. WEBB’S
new nebula in Cygnus, and have sent him drawings of the field, which
he confirms. I have also made some fine drawings of Jupiter and
Mars. On December 12th, 11 p.m., I tackled σ 749 (in Taurus), a very
difficult test for my aperture, only 0·8″, and _perfectly_ split it
with power 300. The night was superb. When you consider that the
theoretical limit of dividing power for a 6-1/2″ is only 0·7″, I
think I have done well to split a star 0·8″ in our climate.
Faithfully yours,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From_ G. FERGUSON, Esq., M.D.
ALTIDORE VILLA, PITTVILLE, CHELTENHAM,
_June 26th, 1879_.
MY DEAR SIR,—I write to tell you that Thursday night being very
fine, I had a good opportunity of trying the (an 8-1/2″) mirror on
Jupiter, although this planet was lower than it should have been to
give the fairest trial. Well, I can only assure you that, despite
the low position, I never saw it so beautifully before. The contour
of the clouds, particularly one orange one, _sf_, the delicate
lines, and the colouring of the belts, were all seen with a
sharpness which I had believed scarcely attainable, and proving that
the result of your labours has been to effect a very real
improvement in the speculum. Notwithstanding the good planetary
definition, the air was not tranquil enough for seriously attacking
really difficult doubles; still I was much pleased with its
performance on π Aquilæ.
Yours truly,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From the same Gentleman._
_July 27th._
Yours of July 25th duly to hand. I have the speculum adjusted in the
“pink” of accuracy. Star discs are small and round, with concentric
diffraction rings, and quite rayless except in the case of the very
brightest stars, and even with these the rays are very trifling. But
for the diffraction rings, which I fancy a really good night will
mostly get rid of, I should, I feel sure, have readily divided η
Coronæ.
The Moon last night, though very low, was seen with most gratifying
ease and sharpness. Altogether you will gather that I am more than
satisfied. I am greatly gratified, and will look forward to great
pleasure as the season advances.
Yours faithfully,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From_ THE REV. JEVON J. MUSCHAMP PERRY, M.A., F.R.A.S.
ST. PAUL’S VICARAGE, ALNWICK,
_August 8th, 1880_.
MY DEAR SIR,—You have indeed surpassed yourself, and your
performance is better than your promise. The mirror arrived safely
yesterday, and when I unpacked it I was exceedingly pleased with its
surface and general appearance, but of course that was a small
matter. I waited till night to test it on a close double.
I first tried it on ε Boötis, and although the night was very bad
the definition it gave of the two stars with 450 and full aperture
was admirable, considering the night. After waiting a long time for
clouds to clear away, I turned the tube on that exceedingly
difficult test, δ Cygni. I consider this star to be one of the
severest tests for any telescope, reflector, or refractor of any
aperture in the whole heavens. The performance of the mirror upon
it, with the _full_ aperture, was simply MAGNIFICENT, the small
close companion standing out clearly, well separated from its bright
primary, although the night was not good. I hardly thought it
possible that the fine 18 inch mirror could be excelled. I am bound
to confess that you have excelled it.
To say that I am extremely grateful to you is a very poor expression
of my feelings. I am pleased and delighted _beyond measure_ with the
_super-excellent_ 18-1/4 in. mirror you have sent me. Clouds put an
end to my work last night, but I have no doubt that in the future
every night’s observations will only accumulate proofs of the
exquisite perfection of your handiwork.
Very faithfully yours,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_Extract from the “English Mechanic,” September 3rd, 1880_.
“The telescope is a silvered-glass Newtonian reflector. There are
two specula, one of 18 in. in diameter, figured by the celebrated
WITH, in 1878, and is a magnificent specimen of that eminent maker’s
handiwork. In fact, I am given to understand that Mr. COOPER KEY
considered that he had attained perfection in this mirror, and of
all men then living there was no better judge than he. The other is
18-1/4 in. in diameter, and was originally figured by Mr. COOPER KEY
himself; but it was only perfect over the interior 14 in., and,
consequently, while the whole aperture could be used on the moon and
planets, this was all of it that could be used upon close doubles. I
determined, therefore, to give this mirror to Mr. CALVER to
re-figure, and, if possible, excel Mr. WITH’S speculum.
“In order that Mr. CALVER might know the extent of his task, I
returned home through London and Chelmsford, bringing with me both
mirrors, which Mr. CALVER tested for himself at the centre of
curvature. After the trial was over, he pronounced Mr. WITH’S mirror
to be an exceptionally fine one, and heartily congratulated me on
the possession of such a beauty. I left the other one with him to be
re-figured.
“And now to come to the most important part of all—the performance
of the 18 in. WITH mirror upon close double stars. Since the
telescope came into my possession, I have never had a thoroughly
good night; but even on an indifferent one, I have, with the _full
aperture_, divided such extremely difficult tests as η Coronæ, μ^2
Herculis, and δ Cygni; and these results were quite sufficient to
show me that the very high reputation of its excellent maker is
worthily and proudly maintained by this mirror. In fact, the
definition it gave one night, when the Scottish Astronomer Royal was
staying with me of ε Boötis, was such, that the Professor
told me I could not expect any telescope, reflector, or refractor,
upon the same object, and on the same night, to do better. However,
I knew Mr. CALVER was doing his very utmost in the honourable and
praiseworthy competition to attain perfection, to give me a mirror
which would bear favourable comparison with Mr. WITH’s. It reached
me about a week ago, and on the same evening I had an opportunity of
testing it upon what I consider to be one of the very severest tests
that can be applied to any telescope, reflector or refractor, in the
northern heavens, that is δ Cygni[3]. To make the test as severe as
possible, I applied the _whole_ aperture at once, with a power of
347. I was surprised and delighted _beyond measure_ with the result.
The small star stood out clearly separated from its bright primary,
and there were two or three diffraction rings round the latter
_unbroken_ in any part, and _equally_ bright all round. I consider
the results which Mr. CALVER has attained in this mirror cannot
possibly be excelled. I measured this star on two separate nights,
and the mean results are pos. 328·9°, dist. 1·29″. I also measured,
with this mirror, another difficult star of the same character,
namely, with a bright primary and small companion, ζ Herculis, with
the following results, pos. 111·3°, dist. 1·03″. I make the
companion of this star a dusky blue, or lavender. As regards the
light-grasping power of the mirror, I turned it, the other night, on
the minute pair between β^1 and β^2 Capricorni, which Sir John
Herschel gave as the test of the power of any telescope and eye to
observe the satellites of Uranus. The night was very unsteady, but
the minute stars of the pair were most conspicuous.”
Footnote:
[3] NOTE.—Mr. Perry does not mean that δ Cygni is one of the most
difficult tests as regards the distance of the components. He has
often seen it with his 6-1/2″ Silvered Glass Reflector, and even
with a stop of 5-1/2″ on the same instrument; but he was surprised
at the beauty and perfection of the images—perfect and unbroken
rings—and he knew that these appearances could not have presented
themselves had not the _figure_ of the mirror been of extraordinary
perfection.
* * * * *
_From_ THOS. WESTLAKE, Esq.
FORDINGBRIDGE,
_June, 1880_.
MY DEAR SIR,—I wrote you last evening, and afterwards had my first
trial with the telescope (a 10 in. Alt Azimuth). It turns out a
beauty. I had the full aperture on all the evening, the air was very
good, but not perfect. Alpha Lyræ was a splendid object with all
powers, a most brilliant disk with just indications of circular
rings—no wings or rays. I turned it on B Cygni, and the beauty of
the mirror stood revealed, both stars _perfect disks_, with _just_
the indication of perfect circular defraction rings, and the colours
were most beautiful,—nothing could possibly appear finer. I consider
the mirror perfect, and the stand most convenient and smooth and
pleasant in action.
I am, dear Sir,
Yours truly,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From_ THE REV. E. H. LOWE.
WILMCOTE,
_April, 1880_.
DEAR Mr. CALVER,—I have been exceedingly occupied, as there has been
a succession of gloriously fine nights, and I have secured the
Nebulæ diagrams I so much wished for Mr. WEBB,—and I would allow
nothing to divert me from them—but I put it (a 15-1/2 in.
equatorial) on Zeta Cancri, and it was shown beautifully. I have
been working at the driving clock, and it is under capital control.
The great cluster 13 M., is a glorious object, and magnificently
resolved. I see all I look for on the Moon.
Faithfully yours,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From_ W. SCOTT, Esq.
SOUTHWICK, SUNDERLAND,
_July, 1880_.
DEAR SIR,—Dr. Blacklock, and also Mr. Bell, have seen the mirror,
and pronounce it perfect, and it performs admirably.
Yours truly,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From_ JAMES L. MCCANCE, Esq., F.R.A.S.
PUTNEY HILL, S.W.,
_October 23rd, 1879_.
DEAR Mr. CALVER,—Weather and circumstances have been very
unfavourable for doing much work with the 10 inch reflector since I
got it from you. But with what I have seen with it I am very
pleased; in good weather the views of the planets, Jupiter and his
“Great Red Spot” especially, were grand. The mounting (equatorial)
is quite satisfactory, and the movements work smoothly and well.
Yours very truly,
(_Signed_.)
* * * * *
_From_ FRANK C. DENNETT, Esq.
10, TERMINUS TERRACE, SOUTHAMPTON,
_July 11th, 1880_.
DEAR SIR,—It is a long time ago that you asked me to write and let
you know how I liked the 9-1/2 in. I have not done so because I
wished first to see what was to be made of the planets.
Last night, at 14^h 30^m, I had my first peep at Jupiter through it,
and a grand sight it was; his belts coloured, though not so vivid as
they are sometimes, were fine in the extreme; and, though the power
employed was only the achromatic 215, the satellites were beautiful
little discs, one especially showing the tint of its surface.
A quarter of an hour later Saturn was in the field of view; a grand
object, several of the satellites surrounding it. A little cloud was
coming up over it, so I could not see so much of this planet as I
should have liked, though amply sufficient to prove incontestably
its high class.
With double stars I have not attempted much, though on turning it on
μ^2 Boötis I found the division easy, the components being
respectively slightly orange, and dullish white or pale yellow.
I have had lots of grand views of the wonders of the “star depths,”
clusters, and nebulæ, notably 57 Messier, the Ring nebula, in Lyra,
the great Orion nebula, and the marvellous Whirlpool nebula, the
chief outlines of which were well shown.
Hitherto the instrument has been chiefly employed on the Moon, the
details of which come out hard and sharp in a beautiful manner, with
all powers up to 515, the highest I have.
The 5-1/4 in. pleased me very much, but the 9-1/2 in. delights me.
Yours faithfully,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From_ G. W. ROYSTON PIGOTT, Esq., M.D., F.R.S., F.R.A.S., &c.
EASTBOURNE,
_July, 1880_.
DEAR SIR,—There has been but little weather for testing. Mr. Slack
has been staying with me; we are delighted with the 8-1/2″, and
think it a great beauty. I can hardly imagine any mirror much
better, and I expect great precision from it. I find its focus to be
65 inches, not quite so much as my fine Dollond glass, of 3-3/4 in.
aperture.
Yours truly,
(_Signed_.)
Mr. G. CALVER.
* * * * *
_From_ A. WILLIAMS, Esq.
CLARENCE LODGE, GRAFTON STREET, BRIGHTON,
_August, 1880_.
DEAR SIR,—I had intended writing to you to express my pleasure in my
5-1/4 in. telescope nearly a month ago, but thought I would have
another look first, and the more I look the more I am pleased with
it. I cannot now imagine anyone preferring a 3-1/4 in. refractor to
one of these. I have had no trouble at all with the adjustments, and
if was to get out of adjustment, it could be rectified in about five
minutes. Notwithstanding the unsettled weather (giving on an average
only about one fine night in eight), I have examined nearly two
hundred double stars in the last three months, some of them very
difficult. I enclose a list of a few, which will show very well the
capabilities of the instrument.
Yours truly,
(_Signed_.)
Mr. G. CALVER.