Advance of Science, British Association Report for 1854, Part 2, pp. 10-12
[Transactions of the Light, Heat, Electricty, Magnetism section]
On Photographs of the Moon and of the Sun. By the Rev. J. B. READE, M.A., F.R.S.
The author recounts in the first place the prominent results of several trials to obtain photographic pictures of celestial bodies, previous to Mr. Whipples success in 1851, and then proceeds to phænomena which have fallen under his own observation.
The two daguerreotypes of the moon, an original and a copy, which illustrate this paper, will be examined with some interest by the Section. The fainter picture, produced by the moon herself, in the focus of Bond's refractor, was taken in America. It possesses a very remarkable, but latent sharpness, which, however, is so scarcely visible to the eye, that to ascribe to it this character may almost provoke a smile. The proof of its having such a property is furnished by the beautiful copy of it of the same size, which my friend, the Royal Astronomer for Edinburgh, obtained by throwing strong sunlight upon the moon's daguerreotype picture of herself, and obtaining a reverse solar impression of it in a common camera, the conjugate foci being equal. The tones of grey and yellow which mark the action of the moon. become, when handled by the sun, fine contrasts of black and white. The mountain chain round the portion of the Mare Imbrium, is finely given in the copy, though it almost requires a stretch of the mind's eye to discover some of the details in the original. The well-known ray of light from Menelaus passing through the centre of the Mare Serenitatis, is another point of striking contrast in the two pictures, as well as the outline of the shadows in several of the craters. It is said that Lord Rosse was much interested with this happy experiment by Prof. Piazzi Smyth, as it tended to solve a question which had often occurred to him respecting the probable beneficial use of penetrating sunlight under such circumstances; and in this point of view, it is well worthy of being recorded. Two Calotype examples of selenography form additional illustrations of this paper. The small moon, fastened on a corner of the larger picture, was taken by Mr. Henry Pollock with a double combination of short focus, and in less than a second. The bright point of Tycho, though on so small a scale, is well marked at the top of this minute Calotype, and the seas, to which I have already referred, give their more sombre reflection at the bottom. This is chiefly of interest as showing the decided energy of a power which in former years was supposed to be absent.
The more important drawing is a large positive picture of the full moon, nearly nine inches in diameter, and therefore on a scale of about 250 miles to the inch, of which the negative was taken, on the 6th of September, in the focus of the Craig telescope, at Wandsworth, whose diameter is 24 inches and focal length 77 feet,— and when I state that it is the first attempt, it will be received, notwithstanding certain imperfections of manipulation, which are not concealed by artificial tinting, as a step in the right direction. All the more important features of the moon's surface will be discovered by those who are familiar with their telescopic appearance, and the portion of the eastern hemisphere admits of interesting comparison with the sun's daguerreotype copy already described. We find in both, and with almost equal distinctness, the Mare Crisium with the bright surrounding country which separates it from the Mare Foecunditatis and Mare Tranquillitatis to the south and west, — the Crater Menelaus with the ray already spoken of, — the semicircular ridge round the Mare Imbrium, and the unreflective crater, Plato, at its north-west extremity. Ou the western side, we have the bright Aristarchus, Kepler, Copernicus, and Tycho, with the streams of molten lava extending over the southern hemisphere ; but owing to the phase of full moon, the craters and mountains are not relieved by shadows. The time of exposure of the collodion negative was thirty-five seconds; but it is evident that Tycho and the brighter portions are overworked. In the absence also uf an equatorial mounting, perfect steadiness could not in the first instance be secured. Mr. Gravait applied a micrometer screw to the eye end of the telescope, and turned it with a winch handle, and when the moon was on the meridian this was almost tantamount to an equatorial motion for the space of thirty-five seconds. A fine wire stretched across an aperture in a slip of wood was placed close behind a negative when in the focus of the telescope, and Mr. Gravatt found that by humming a tune he could turn the handle of the micrometer so steadily as to keep Aristarchus continually bisected. Mr. Prout, who prepared the collodion surface, unfortunately counted the seconds too loudly for the man at the wheel, and hence arose a little cause of unsteadiness, which was afterwards prevented by my attending to the time of exposure instead of Mr. Prout. Collodion pictures of the moon, as well defined as her image on the ground glass, and taken through all her phases, would leave scarcely anything to be desired in consequence of the magnifying power of the object-glass itself; and future experiments will be directed by Mr. Craig into this channel.
On the night of the 11th of September, we renewed our attempt when the moon was in a more picturesque position; but an undetected source of error, and the increasing density of the fog when the moon was on the meridian, prevented us from procuring a successful negative. Moreover, the true photogenic focus has not yet been obtained by means of sulphate of quinine. I may state, however, that the division in Saturn's ring, the slate-coloured ring, and the inner satellites, were well brought out with my solid eye-piece, under a power of 300; and α [alpha] and ε [epsilon] Lyrae, with their minute companions, were also well exhibited. In fact, the present superiority of the telescope, though confessedly admitting of improvement in figure, consists in its command over the faintest points of light. That so large an object-glass, worked at a mechanical disadvantage by hand, and not machine polished, should do so much in its first offer to the stars, is far from discreditable to those who calculated and ground the curves; and the errors, which are now known and estimated, will be corrected by reworking the surfaces on the plan adopted by Lord Rosse and Mr. Lassell. On the 12th, the morning following, I endeavoured, with Mr. Gravatt, to take the sun on the meridian, and on the same scale as the moon; and I succeeded by an instantaneous operation in exhibiting, in the negative, the peculiar mottled character of the surface which is usually brought out by high magnifying power. Dr. Diamond, who printed the positive of the moon, found the sun picture, however, rather overdone for transferring.— It will be necessary, therefore, either to use collodion and nitrate of silver simply, without any or but little sensitive solution, or else to pass the sun's rays through some coloured glass, which will partially retard their energy. A series of pictures of the spots on the sun, as well as of the general surface, may then be successfully obtained; and hence it is not too much to anticipate some accession to our knowledge of the physical character of both our great luminaries by means of this gigantic telescope, which Dr. Diamond enables me to exhibit photographically to the Section.
The Rev. Craigs telescope at Wandesworth Common in west London was featured in The Illustrated London News of 28 August 1852.
An interesting account of Astronomical Photography in the 1850s was given by Reades associate Dr John Lee when president of the Royal Astronomical Society in 1862: [Dr Lees address].
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