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Admiral Smyth’s - Sidereal Chromatics

PART II. (b.) (cont.)


The Hartwell Experiment.

We tried an experiment on chromatic personal equation, in its simplest form, at Hartwell, on a fine evening, the second July, 1829. Having repaired a stone pedestal in front of the south portico of the house, on which was placed a Gregorian telescope of 5½ inches aperture, a party of visitors, consisting of six ladies and five gentlemen, were invited to gaze upon the double-star Cor Caroli; and they [*50] were each to tell me — sotto voce to prevent bias — what they deemed the respective colours of he components to be. The first who stepped out by request, was my good friend the late Rev. Mr. Pawsey — more addicted to heraldry than to astronomy — who, after a very momentary snatch, flatly declared that he could make out nothing particular: but the other spectators were a little more attentive to the plan proposed, and their respective impressions were thus noted down in the large Hartwell Album:-

Miss Tyndall A. Pale White B. Violet tint
Mrs. Rush A. Yellowish cast B. Deadish purple
Miss Honor A. Yellowish B. Lilac
Miss Charlotte A. Light dingy yellow B. Lilac
Miss Emily A. White B. Plum colour
Miss Mary Anne A. Paleish yellow B. Blue
Mr. Rose A. Cream colour B. Violet cream
Mr. B. Smith A. Pale tint B. Darker blue
Dr. Lee A. Whitish B. Light Purple
Capt. Smyth A. White B. Plum-coloured purple

Now, whatever may be said about instrumental means, tendency of metallic mirrors, weather influence, atmospheric light, or the objects position as to meridian, it is clearly obvious that every condition was common to the whole party, and we doubtlessly all meant the same hues. It must be admitted, however, that the stars were new to most of the spectators, and, though some of the eyes were surpassingly bright, they had never been drilled among the celestials. Further observation, with an achromatic instrument, led me to record Cor Caroli in the Cycle for 1837, A flushed white, and B pale lilac; but, as Sestini found them to be yellow and blue in 1844, I again probed them in 1850, when A struck me as full white and B very pale but slightly ruddy under that paleness. From the lightness of the tints, this object offers less distinctness than deeper-coloured stars ; insomuch that in 1830 Herschel said — With all attention I could perceive no contrast of colours; yet, at my last [*51] inspection in 1855, three observers were unanimous that A appeared to be a pale reddish white, and B lilac, under a magnifying power of 240, and a fair sky. All this shows the urgent necessity of a chromatic scale being drawn up for general adoption; and that, as yet, we are only on the threshold of a very beautiful department of knowledge.

Mistaken notion.

Many persons may think that a mere glance at colours is enough to impress them at once on the memory, and that, without any practice at that sort of remembrance, they can keep any tint in their mind for a length of time; but a more erroneous idea was never entertained. To these unhappy persons greens are greens, and blues blues; for they heave never entered the magical region of colours, whereby a whole world of intellectual enjoyment is for ever closed against them. Bring them to the proof of their boasted powers; show them any portion of a landscape; and then place colours before them, and make them put down the various tints from memory, but this a week or two after the scene was witnessed. If hardy enough to attempt the task, every one of their tints will be found in error, and they will only put down one where nature had fifty. Even the painters confess, that, though colour may be a low branch of their art, yet it is the most difficult. Just look at the walls of the Royal Academy and see how rarely is a good colourist to be met with, and, when he is, how the initiated will gloat over the matchless and magic variety and mellowness of tints, while the uninitiated can see barely more than one, and that to them not noticeably different from the world of common-places beside it. Only look, too, at the characteristics of those painters who draw from nature, but do not colour also from her; who make their sketches in the open air with pencil or sepia, and fancy colouring to be so simple and so easily remembered, that they may do that afterwards comfortably at their home. Such works are detected wherever they are seen, by the poverty of tights, and by the uniformly monotonous colours that are always employed in the same manner. The human mind cannot invent to any extent, but can merely [*52] put together in a novel manner materials collected from the external world. Hence such materials in colouring can only be impressed on the memory by actual pains-taking and labourious copying and working from nature, by making the tints and applying them in imitation of her. By such training, this branch of memory may be strengthened as well as any other; for we find that the works of artists who adopt this method are always superior in their colouring to those of ethers, even when they paint from retentive memory or imagination. And one of the best colourists that we have ever had in landscape-painting was so impressed with the importance of cultivating the memory in this manner, that he used, even in the days of his prosperity and highest prices of his works, to spend much time in the open all-making studies in oil, and then, as soon as they were made, tore them up; so that, as the followers of Cortez saw the necessity of conquering when their commander burnt the ships in which they might have made an inglorious retreat, and exerted themselves accordingly, — in the same way, not being able to refer, when painting a picture at home, to the sketch made in the open air, he felt himself necessarily obliged to tax his powers of memory, and make them exert themselves to the very utmost.

Signor G. Lusieri.

In the early part of this century, it was my good fortune while in Athens to make the acquaintance of the late Signor Gianbattista Lusicri, the eminent landscape-painter engaged by Lord Elgin to work in Greece. This philosophical artist showed me a series of views, proving his gradual improvement through twenty years, by making Nature his model throughout; and he restricted himself, moreover, to the same hour of the day for colour; so that some pictures which he was unable to complete before a change of weather, he reserved tilt the same season of the following year. Hence in great measure arose the perfection of his pencil.

Spectral lines.

The second, or instrumental, method of determining colour, need not be entered upon at much length here, as mere amateurs are not very likely to practise it; and would be [*53] working at a great disadvantage compared with any instrument in a public observatory specially devoted to this object-
Brightness is everything under such appliance, and this must be commanded both by elevating the telescope into a high region of the atmosphere, and by adopting the largest possible size of aperture; for, not only must photometrical determinations of the lucidity of different sections of the spectra of stars formed by prisms be made, but the black lines in the spectra of each star must also be carefully examined into, as all the transcendent intelligibility of modern optics depends on them. Still the task appears to be equally prolix and toilsome; and, moreover, spectrum explanations are much more fatiguing to the eye than ordinary telescopic work while it is only on the finest nights that the lines in the stellar spectra are steady enough for measurement. Indeed the difficulties of observation are now so complex, that the complete scrutiny of the spectrum of a single star may probably be the work of some years. [10]

Wollaston and Frauenhofer.

It is under no depressing view of the effects of progress that I perceive, however anticipations may be indulged in, the alliance between Astronomy and Chemistry is not yet definitively ratified so that at present it is rather perplexing to speculate upon the ultimate results of the connection. Suffice it here to note, it is to my late eminent friend Wollaston that we owe the discovery of the existence of a peculiarity in solar light, which reveals the deficient rays causing the black lines of the spectrum: and this was followed quite independently by the marvellous measures of them by Frauenhofer and of Munich, whose accurate determinations of their distances now form standard points of reference for apportioning the refractive powers of different medico on the rays of light. These opera-lions opened out away for the masterly metallic investigations of Kirchhoff and Bunsen. Such skilful and well-conducted researches [*54] are pregnant with the best augury; and the elaboration of successive variations of them must infallibly aid our future advance in the knowledge of STELLAR PHYSICS.

Advantages of instrumental method.

There is still, however, much to achieve before full reliance can be indulged in, as well respecting drilling the eye as the manufacture and use of its apparatus, and the subsequent delicate manipulation. When genius and perseverance shall have brought these conditions to bear in concentrated practice, then will this instrumental method of reducing colour to brightness and place prove invaluable; because — in addition to the exactness of the numerical determination of which it will then be capable — it would further overcome a most serious source of error — one which has barely been touched upon in all that has gone before in this our lucubration, and may affect to its fullest extent the method of the senses, namely, chromatic personal equation. In fine, it seems destined to become another means of augmenting the debt which pure Astronomy ewes to the powers of practical observation — which is the basis of all we know in the argument.

Proposed diagram of colour.

The instrumental desiderata above alluded to are mostly, as yet, irreducible to general practice, especially upon minute or dim objects; and, therefore, until certain difficulties shall be overcome, the amateur may still render good service to the cause, by noticing the stellar hues according to the scheme of colours submitted to him on the chromatic diagram appended. Where the mental impression is not quite adequately represented by these tints, it can be modified by an expressive adjective, as blueish green, brownish yellow, and the like; but, in pronouncing upon very delicate distinctions, the observer must keep in mind that all colours are accompanied by their accidental or opposite tinctures, or those which depend on the affections of the eye, rather than on the light itself — and, when the direct and accidental colours are of the same intensity, the accidental is then called complementary, because completing the series with the direct hue.

The very numerous shades from white to pale yellow are so [*55] unfit for representation and lamplight reference, that they are omitted in the annexed form; but the careful observer may readily estimate the intensity of almost colourless bodies according to the following order — Creamy white 1, Silvery white 2, Pearl white 3, and Pale white 4.

Notwithstanding the amount of obstacles that I have mustered up, they are not insuperable to resolution ; for, as in mundane affairs, the word impossible ought to meet with no encouragement in scientific emprise. A specimen of the advantages of a more exact method than that which has hitherto obtained among us, may be here given, as showing that the glow ascribed can readily be consulted, which the mere guessing cannot. Indeed, if memory is to be trusted so for, some notations on the old system may be contrasted with our proposed plan, thus —

STAR CYCLE DIAGRAM
51 Piscium A. Pearl White B. Lilac tint A. White 3 B. Purple 3
γ Andromedæ A. Orange colour B. Emerald green A. Orange 2 B. Bluish green 3
40 Persei A. Pale white B. Ash-coloured A. White B. Blue 4
225 P. Aurigæ A. Creamy white B. Pale grey A. White 1 B. Blue 4
δ? Hydræ A. Light topaz B. Livid A. Yellow 4 B. Purple 3
17 Virginis A. A. Light rose-tint B. Dusky red A. Red 4 B. Red 3
ι Boötis A. Pale orange B. Sea green A. Orange 3 B. Green 4
α Herculis A. Orange B. Emerald, or bluish green A. Yellow 2 B. Blue 3

Instance of β Cygni.

By the adoption of the new and firmer method of registry, many of the differences now on record may turn out to be more apparent than real, and will probably disappear before the organised process of using an accepted chromatic scale with educated eyes. We have alluded to the otherwise complicated embarrassments and uncertainties incident to this kind of observation; yet still there is basis enough to inspire the warmest hope for exertion. The beautiful pair of stars forming β CYGNI may be cited as a strong instance in point of [*56] the agreement of many eyes and instruments, even by the prevalent rule-of-thumb system; because that object has an advantageous position in altitude when on or near the meridian, to facilitate this branch of inquiry. It will be borne in mind that β is an optical pair; for, as I have elsewhere remarked, strong colours in the pulcherrima of the heavens are not at all indicative of motion. To moderate the ordinary complaints about bias, magnifying power, aperture, achromatism, spherical correction, and local atmosphere — and to test the merit of gazing with all its imperfections on its head — the eyes and telescopes of various observers, at various places, have been summoned in aid; and the results of the requisition are to the following effect:–


OBSERVER DATE RECORDED COLOURS PLACE
Sir William Herschel 1779 A. Red [11] B. Blue Slough
Sir William Herschel 1781 A. Pale red B. Beautiful blue Slough
Sir William Herschel 1783 A. Red or orange B. Blue Slough
Sir John Herschel 1816 A. White, or yellowish white B. Blue Slough
Sir John Herschel 1830 A. Yellow B. Blue (superb) Slough
Herschel and South 1822 A. Yellow B. Blue (strongly contrasted) Slough
Admiral Smyth 1830 A. Bright yellow B. Fine blue Bedford
Admiral Smyth 1837 A. Topaz yellow B. Sapphire blue Bedford
Admiral Smyth 1849 A. Golden yellow B. Smalt blue Bedford
Admiral Smyth 1857 A. Orpiment yellow B. Turquoise tint Bedford
Mrs. Smyth 1830 A. Fine yellow B. Blue Bedford
Mrs. Smyth 1857 A. Orange yellow B. Greenish blue Bedford
Struve the Elder [*57] 1832 A. Yellow (colores sunt insignes B. Ceralean blue Dorpat
Benedict Sestini 1844 A. Orange gold B. Azure Rome
Piazzi Smyth 1856 A. Pale yellow B. Blue Teneriffe
Piazzi Smyth 1862 A. Yellow B. Bluish Green Elchica
Padre Secchi 1857 A. Reddish yellow B. Green (fine colours) Rome
Rev. W.R. Dawes 1857 A. Orange yellow B. Greenish blue Haddenham
Rev. W.R. Dawes 1857 A. Crocus yellow B. Greenish blue Haddenham
Isaac Flectcher 1850 A. Yellow B. Blue Tarn-bank
Isaac Flectcher 1857 A. Rich yellow B. Brilliant blue Tarn-bank
Isaac Flectcher 1864 A. Rich yellow B. Greenish blue Tarn-bank
Mrs. Flectcher 1850 A. Fine yellow B. Bluish green Tarn-bank
Lord Wrotesley 1857 A. Golden yellow B. Greenish blue Wrottesley
Lord Wrotesley 1857 A. Reddish orange B. Clear blue Wrottesley
Captain Higgens 1864 A. Golden yellow B. Bluish green Bedford
Rev. T.W. Webb 1849 A. Fine yellow B. Ultramarine blue Hereford
Rev. T.W. Webb 1849 A. Fine yellow B. Aqua colesti blue Hereford
George Knott 1864 A. Golden yellow B. Bluish green Cuckfield
Mrs. Knott 1832 A. Variable, with ruddy cast B. Emerald green Cuckfield
Dr. Lee [*58] 1832 A. Orange tinge B. Bright blue Bedford
Dr. Lee 1864 A. Pinkish yellow B. Cerulean blue Hartwell
Mrs. Lee 1864 A. Orange B. Green Hartwell
Sir Rowland Hill 1864 A. Yellowish orange B. Bluish green Hartwell
Lady Hill 1864 A. Yellow orange B. Green Hartwell
W.R. Birt 1864 A. Yellow dashed with orange B. Clear pure blue Hartwell
Samuel Horton 1864 A. Fiery yellow B. Sky blue Hartwell
William Huggins 1864 A. Yellow B. Blue Tulse Hill
J.R. Hind 1864 A. Pretty deep yellow B. Sapphire blue Twickenham
C.G. Talmage 1864 A. Straw-coloured B. Blue Twickenham
Frederick Bond 1864 A. Pale yellow B. Light emerald green Birmingham
Rev. Robert Main 1861 A. Yellow B. Blue Oxford
Rev. Robert Main 1861 A. Orange B. Sea green Oxford
Mrs. Main 1864 A. Orange B. Sea green Oxford
Rev. G. Fisher 1864 A. Bright orange B. Violet Hartwell

Replies to my request.

In this enumeration all those observations given after the year 1856 were specially noted at my request — a request always acquiesced in with kind readiness by the parties addressed; and, as some of the replies contain matter in illustration of the recorded facts, the reader shall be treated to a few extracts from them in the order in which they were received.

Sir John Herschel.

Sir John Herschel, in answer to my inquiries, states — under date July 4th, 1864 - From general recollection of the object when looked at, I should certainly say the observation of [*59] November 3rd, 1816, does not make the large star enough coloured. And, to a query regarding one of Sir Williams epochs, his son has since informed me, that he copied verbatim what he found written as to β Cygni in the registered sheets taken from his father’s diaries. The excerpt, which is valuable in this relation, stands thus :–

Sep. 12, 79. Two fine stars. One red, the other blue.

Sep. 6, 81. The large star (pr.) pale red, nlsi pretty red. The small, a beautiful blue. 227; under 460, estimation of colours the same.

Feb. 8, 83. Large, red or orange. Small, blue or purple.

The Rev. W. R. Dawes.

The Rev. W. R. Dawes, in a letter of July 5th, 1864, says — I succeeded last night in getting some very satisfactory observations of β Cygni for the colours of the components. I examined them with powers from 93 to 890. With 93, 153, and 258, I pronounce the colours to be

A. Golden yellow. B. Greenish blue.

With powers 405, 557, and 890, they appeared

A. Golden yellow. B. Slightly more of a greenish tinge than with the lower powers.

With one of Horne and Thornthwaites so-called Aplanatics — which is certainly as achromatic as possible in all parts of the field — power 302, the colours were precisely the same as with the lower powers above quoted. Each star being alternately concealed by a small field in my solar eye-piece, the colours remained the same, so they were also with a perforated diaphragm over the whole object glass. For comparison I noted the colours of the components of α Herculis —

A. Light orange. B. Blue-green.

Compared with β Cygni,

A is rather redder, and B rather, greener.

The night was favourable for such observations, being free from haze, and calm. The scarcely varied colours with the highest powers compared with the lower, arises I doubt not from the fine correction of this object-glass, which is not over-corrected. In the violently over-corrected Munich ones there is great difference between the high and low powers. Mine [*60] is, I think, almost exactly like your old Bedford favourite in respect of correction.

The same post also brought me dispatches of the same date and on the same subject from my friends Captain Higgens and the Rev. T. W. Webb. The Captain informs mc, that, after the spell of cloudy weather which we have had so long, I almost despaired of being able to see the stars last night; but a clear came on before sunset, and as the darkness increased the definition became very good. I think I never saw Jupiter so well before at so low an altitude as I did soon after sunset. As the night advanced objects became at rimes a little blotty, but on the whole we had a good time of it.

We had a long scrutiny of β Cygni. My wife sees the pair as follows: A golden yellow; faded sapphire blue; while I make A golden yellow, and B bluish grey. I have no doubt we mean the same tints.
I am sorry that I have not looked at this object oftener, I see a note in my log of May 24th: A golden yellow, B faintish blue, and I cannot help thinking that the colour of the latter is not so vivid as I saw it last year. I shall keep it well in sight during the remainder of its appearance. We looked. at it with 115 to 200 (Cooke’s 4-inch, 5-foot focus), which arc the powers best adapted for my telescope for ordinary objects when testing colours.

The same night, July 4th, Captain Higgens turned his instrument upon 95 Herculis charged with magnifying powers of 115 and 200; the definition was good, and the normal colours plain, but faintish.

The Rev. T. W. Webb.

The Rev. T. W. Webb entered warmly into the question, saying; We have had such a prevalence of cloud of late, that, although I determined to take the very first opportunity of attacking your object, I feared it might be long deferred. Last night, however, proved unexpectedly clear, and I set to work at once, and with various powers — 65 and 111 Ramsden, 170 Huyghens, 264 single lens, 323 Steinheil, and 600 Huyghens, and macro-micro — I had the same result, which was [*61] quite independent of your own estimates, as I had forgotten their precise terms. A appeared to me a full yellow, varying to topaz, B an aqua colestis blue, with a very slight tinge of green.

By aqua colestis- an old alchymical name which I picked up I know not where — I mean the splendid blue produced by adding ammonia to a solution of sulphate of copper, - ammoniuret of copper is, I fancy, its chemical name. The star reminded me at once of this, only in comparison its blue appeared a trifle greener. This comparison is made from memory only, as I have not seen any of the liquid so called for years, and have not the materials for making it at hand.

Chemical tests are of material use in watching the colours of stars, since they can be made and adapted at all times, and, generally speaking, in all places.

G.Knott.

Mr. George Knott, who complied with my request (July 6th) as a most pleasant duty, reported in these terms: On Monday evening at about 11 oclock the clouds cleared off, and, accompanied by my sole assistant, Mrs. Knott ( an astronomers best assistant as I think the talented Astronomer-Royal for Scotland says somewhere), I adjourned to the observatory with a view of attacking the redoubtable β Cygni with my Alvan Clark refractor. The images of the stars were, however, rather confused, and the state of the atmosphere not favourable to colour observations, for which a really fine night seems almost as indispensable as for delicate measurements; but the following are our entirely independent estimates — valeant quantum:-


β CYGNI.

7½-inch Equatorial, full. aperture. Powers 173 and 328 — Thornthwaites aplanatic:-

Mr. Knott

A. Full golden, with orange cast.
B. Fine pale bluish green. Decidedly green.
Mrs. Knott

A. Variable, with ruddy cast.
B. Emerald green.

With the aperture contracted to 3.7 inches, and negative eye-piece of power-258, I thought A full golden, with ruddy cast, and B pale blue green; and my estimates were confirmed by Mrs. Knott. [*62]

Last evening was finer, and I had some very good views of this glorious pair with various powers and apertures, and estimated

A. Full clear golden yellow.
B. Delicate pale bluish green.

With 3.2 inches aperture I thought the colour of B more decidedly bluish, but still with a green cast. In the finder (2 inches in aperture and magnifying power 20) B appeared more decidedly bluish; but in the large telescope, with apertures from 4 to 7.33 inches, its tint was a very delicate and decided bluish green.
To enable you to judge of my colour estimates better, I fixes examined a and 95 Herculis, with the following results:-

α Herculis.A. Golden.B. Greenish blue, deeper in colour than B of β Cygni.
95 Herculis. A. Pale greenish yellow. B. Pale rosy yellow.

On the 10th of August, Mr. Knott wrote to me again, announcing a fresh testimony-
Thinking you might perhaps be interested to learn what could be made of the colours of β Cygni with one of the Silver on Glass reflectors, I wrote to an ingenious correspondent (Mr. Bird of Birmingham) who has a large one of his own make, 11 5/8 inches aperture, and of excellent quality (he discovered the duplicity of the small star following Procyon at a distance near the parallel, consisting of two 9-10 mag. stars, distant from each other about 0.6″), and asked him to oblige me by examining that glorious pair.

I received his reply a day or two ago, and now proceed to quote the ipsissima verba of his report:-

I had several looks at β Cygni for the colours of the stars, and my impression is, that the large star is a pale yellow and the small one a light emerald green stained with blue. The green is very obvious with a large aperture, and the field seems to be tinted with it. Mrs. Bird does not see the green so plainly, but a young lady staying with Its pronounced decidedly for the green, toned with blue. When the stars are put out of focus, the blue seems to be the most prominent. I should esteem it an honour to know that Admiral Smyth was in any way interested in the showing of colours by my silvered-glass speculum and Munich prism, &c. &c. [*63]
Thus the blue green colour of B is quite confirmed. The testimony of a reflector is very interesting on the point.

Earl of Rosse.

Among those whom I petitioned on this occasion was the Earl of Rosse, for I was desirous of obtaining such evidence also as would be afforded by his noble gigantic instruments. Unfortunately for my object, his Lordship was in England, and a letter from Brighton of the 7th of July thus informed me: Although I have so often seen β Cygni with both our telescopes, I have never made any memorandum which would enable me to answer your question. In fact I have merely regarded it as a splendid object for visitors who were not astronomers.

My assistant, I am sorry to say, is now absent at the seaside, being very unwell, and I could not rely upon any of the men about the observatory, as they have merely been trained to work the instruments. The first opportunity we will do our best to answer your question accurately.

I have merely inserted this in order to acquaint the reader that, if Lord Rosses promised appreciation of the colours of this double star comes to hand before the finis of this brochure, it shall be duly appended.

Isaac Fletcher.

Mr. Isaac Fletcher (July 9th) writes from Tarn Bank: Isaac Fletcher. Since I received your request to examine the colours of the components of β Cygni the nights have all been cloudy except last night, when at 10 oclock I levelled the 12-foot refractor at β, and examined the colours with various powers from 134 to 425. I make the colours as follows:-

A. Rich yellow.B. Greenish;

and Mrs. Fletcher’s independent judgment is

A. Fine yellow. B. Bluish green.

Afterwards on referring to the Speculum, Mrs. Fletcher said that Mr. Dawess description of A ascrocus yellow was to her mind exactlyspecified.

Dr. Lee

Dr. Lee, in a report from Hartwell dated 20th of July, [*64] remarks: The colours of β Cygni were observed with a power of 118 on the equatorial instrument, after the stars had been examined under an eye-piece magnifying 50 times. A diaphragm with a wide slit was inserted, by which each star could be examined separately; but no alteration was effected in the estimation of the components as otherwise scrutinized. As you seemed desirous of obtaining the appreciation of various eyes, in addition to those sent to you already, I may add that Miss Wilkinson, and Messrs. Drummond Davis, Douglas Brown, and J. E. Hall, were agreed in pronouncing the colours to be yellow and blue. Mr. D. A. Freeman, however, thinks that the larger star appeared to him red, not deep red; the smaller, under various powers, was light, blue.

With an eye-piece magnifying 240 times, Mr. Birt was impressed with the great purity of the blue of the star B, and on calling it to mind afterwards was disposed to regard it as fine azure: Mr. Horton compared it to the blue colour of the egg of the hedge-sparrow, certainly a rural,- but very applicable, comparison.
That the telescope was in excellent working order was evinced by its sharp definition of the clusters in Perseus, the annular nebula in Lyra, and various parts of the moons surface,- she then being a little after her first quarter. Your two variable stars following 80 Messier have re-appeared, and are duly noted for use.

Sir R. Hill.

Sir Rowland Hill, whom I have long appreciated as an amateur astronomer, [12] thus described the hues ill question: On the 11th of July, we examined the fine double-star β Cygni, the recorded estimates of colour, with power 118, being as under —-

The large star A. Yellowish orange.
The small star B. Green.

A lower power (50) gave a rather bluish tint to the smaller star; but the concealment of one of the stars by a [*65] diaphragm of metal did not alter the previous impressions; thus proving that the colours really emanated from the stars, and were not merely complementary tints.

Lord Wrottesleys.

Besides Lord Wrottesleys colour-notation of July 19th, above recorded, he was good enough to send me the micrometric leg. measures of the angle of position and the distance between the components of β Cygni, as expressly noted by Mr. Hough, his lordship’s astronomical-assistant; and which I received on the 21st of that month. Now as these determinations directly confirm the declared opticity of this object, and therefore Lear out my dictum that vivid colours are by no means indicative of motion, I will enrol them here:

Mag./Colour.
A.
Mag./Colour.
B.
Position W. n. Dist. w. No. of
Obs.
Power Date
1864
3 Pale gold 4-5 Bright blue 56° 28′ 10 34″.532 0.1w. 10 459 July 6
- Light orange - Greenish blue - - - - - - 83 July 8
3 Light orange 4-5 Light blue 54° 28′ 6.8 10 34″.405 6.8 10 450 July 13
3 Golden orange 4-5 Light blue 55° 39′ 5.5 8 34".255 5.1 8 450 July 14

In the above table W. and w. are the sums of the weights assigned to each single observation, divided by 10.

Fixity of β Cygni

The fixity of β Cygni being rather a standard point to establish in stellar Chromatics, we will repeat the results of the former operations, which are extended by reducing right ascensions and declinations into angles and distances, so that Bradley and Piazzi may be received in evidence. The whole presents a singular view of the agreement of various observers and various instruments in different places, and at different epochs, insomuch that ALBIREO must be deemed one of the best determined stars in the heavens, and therefore very fitting for the object before us. Its place in latitude and longitude is, of course, beyond cavil, it being settled by the meridian labours of many public observatories; while the extra-meridional operations exhibit the following deductions:— [*66]

OBSERVER. POSITION. DISTANCE. EPOCH.
Bradley 57° 31′ 34.20″ 1755.00
Hersehel I.. 54° 52′ 34.83″ 1782.45
Piazzi 54° 31′ 34.28″ 1800.00
Struve I. 54° 30′ 34.29″ 1821.76
Herschel II. and South 54° 45′ 34.51″ 1830.54
Dawes 55° 32′ 34.38″ 1822.98
Smyth, W.H. 55° 23′ 34.2″ 1830.81
55° 36′ 34.4″ 1837.58
56° 12′ 34.1″ 1854.67
Fletcher 56° 25′ 34.412″ 1850.83
55° 41′ 34.370″ 1857.42
Lord Wrottesley 55° 26′ 34.557″ 1857.47
Padre Seechi 54° 57′ 34.419″ 1858.29
Smyth., C. Piazzi 55° 25′ 34.59″ 1862.72
Hough 55° 21′ 34.297″ 1864.53
Main 56° 00′ 34.28″ 1864.63

Mean of the above.

The arithmetical mean of which, at the mid-epoch, or 1809.5, gives for the resulting data:
Position = 55° 31″ Distance = 31″.383.

And now I quote myself (Cycle, vol. ii. p. 450) in remarking that these conclusions display a very remarkable constancy both in angle find distance, especially as the two components appear to be affected with proper motions, the amount of which does not differ so much in the several reductions, as in the course of direction of the march. [13] The following are the [*64] inferred present values and signs, and the next rigorous comparison may decide between

PIAZZI. BAILY.
Star A in AR. -0s.07 Dec. +0″.05 Star B in AR. +0s.03 Dec. +0″.12
Star B -0s.13 -0″.01 Star B +0s.05 +0″.04

Mr. Mains recent investigation gives no change in declination for A, and only 0s.002 in AR. : wherefore, considering all the infirmities still adhering to even the best observations, it seems necessary to wait a little longer for absolute conclusions.

W. Huggins.

Mr. William Huggins, of Upper Tulse Hill, wrote to me on the 30th of July, announcing - The earliest possible opportunity to attack β Cygni occurred last night. In a small box, which you will receive by the same post as this note, you will find the colours of β, as they appeared to me, with my telescope, last night. The coloured solutions are to be observed in the dark, by means of the light of a paraffin lamp.

The blue pleases me much — with the yellow I am less satisfied. I tried many other yellow-tinted solutions, but with less success. The brighter star appears less yellow when in tint is not heightened in the eye by the simultaneous view of its blue companion. I estimated the colours by viewing each star separately, and should name the tints:-

A. Very dilute bichromate potassa yellow.  
B. Dilute ammonio-sulphatc of copper blue.

With my new spectrum apparatus I saw separated the spectra of A and B. They differ, as was to be expected, in as marked a degree as do the colours of the stars to the eye. I refrain from describing the spectra at present, as I wish to re-observe them on an evening when the state of the atmosphere is more favourable. The spectrum of B is exceedingly teazing to the eye. It being of the smallest magnitude which admits of analysis by the spectrum with my telescope of eight inches aperture.

Now here is the proof of what has been advancing respecting [*68] being near enough in latitude.the difficulty of making these most delicate observations, for I can aver that the night of the 20th was what a star-meter would call beautiful for micrometric measures, yet the spectrum appliance required the welkin not only to be fine, but superlatively fine. The results, however, when obtained are wonderful: Sirius — a brilliant object for the purpose — displays a spectrum containing five strong bands, and numerous finer lines. The occurrence of sodium, magnesium, hydrogen, and probably of iron, has been negatively detected in that stars atmosphere, which is probably more charged with vapours than that of our sun — a strong argument for the pluralism of Worlds.

The changes of colour which stars of the first magnitude are alleged to have undergone (see ante, page 16) are hinged upon very inadequate bases; but we are preparing to bequeath such matters to posterity in a more tangible and convincing form than has hitherto been known. The effects of light, absorption, and high refrangibilities are now becoming unveiled.

J.R. Hind

Mr. John Russell Hind, on the 2nd of August, says, in answer to my inquiry: I looked at β Cygni this morning, the first opportunity I have had since receiving your note. I make the large star a pretty deep yellow, while I cannot describe the colour of the small one to my vision better than by your term, sapphire blue. Power 70.

Mr. Hind then continues his letter with an interesting bit of intelligence which, though not stringently necessary here, may not prove altogether out of place.
I shall write you about your remarkable companion of Procyon [14], as soon as I receive an answer from Dr. Luther as to the possible error of the elements of Hebe at the time of your observation carried back from the elements of 1847. Luther has Hebe in hand, and I find by careful calculation that she would be within a short distance of the spot where you saw the orange-coloured star, but I believe it is difficult to [*69] bring her near enough in latitude when the longitudes agree. What a sensation you would have created at that epoch (1833) had you recognised this planet!

This would have been a pleasing vision, but that — as I have elsewhere declared — Mr. Fletchers observation of 1850 precludes its indulgence. On consulting this accurate astrometer on the subject, he pointedly says: It is true my observation is a lopsided one, the distance most unfortunately not having been taken; but I have no doubt whatever, and never had any, that the object observed by you in ’33 and by me in ’50 is a star — a variable one, no doubt.

Not long after my observation was made my memory was rigorously ransacked to recall the circumstances attending it. The facts were these: after measuring the position angle, I referred to the Cycle, and, finding my angle nearly the same as yours in 1833, Brought, Well, this is only an optical double star. It is not worth while noticing it any further.

Some one (I forget who) sometime ago suggested that my measure of position referred to a very distant object in the same direction; but I am certain that it did not, for so great difference in distance from your star would at once have rivetted my attention.

On the 4th of August Mr. Hind addressed me again, saying: Since writing to you, Mr. Talmage, assistant in Mr. Bishops Observatory, who is gifted with a remarkably strong sight (though I cannot say how far that may be of service in this case), has examined β Cygni with powers 70, 108, and 200. He calls A straw-coloured and B blue, but not so deep as sapphire blue.

The Rev. R. Main.

The Rev. Robert Main on the 15th of August brought the great Oxford heliometer to bear on the object specially for this record, he having noticed the colours three years before. My judgment, he remarks, is formed by the impression on the eye after forming a single image of each component by making the images cover each other as they now do at the zero, where they are perfectly round. The magnitudes are 3 [*70] and 7 — a good 7. As I thought you would like to have contemporaneous measures of this most interesting star, I proceeded immediately to measure the distance and position, which are as follows: distance by a mean of 10 measures = 34″.28. angle of position = 56° 00′.

The Rev. G. Fisher.

In a report to me of his eye-impression of the hues of the components of β, Mr. Fisher, the well-known arctic astronomer, observes, that to make his estimation of colour be in accordance with Admiral Smyth’s chromatic scale — which he had recorded his observations in Dr. Lee’s book — instead of a bright orange he would have stated the colour of A bright yellow with a tinge of red. This, he continues, affords another instance of the necessity of establishing some well-defined standard scale of colours for such cases, that might be generally accepted by astronomers.

The magnifying powers used were 50, 118, and 240, all of which in harmony as to the actual tints: these were negative eye-pieces, but, from accident, we did not use the single lenses you recommended us to do. From a very slight display of prismatic effect on the evening of September the 5th — which although fine was damp — we were led to suspect a slight deposition of moisture on the object-glass; yet the dew cap was on.

By the enclosed extract which Dr. Lee has sent, you will find that a few nights since his friend Mr. Norman Lockyer pronounced A to be yellow, and B sea-green.

The finding.

On overhauling the forgoing details, and sifting them through a numerical adjustment, it appears that the conclusive finding to be pronounced upon the colours of the star under trial, in general terms, is — according to the tabulated matter -

A. Yellow 3 and B.Blue 2

Now as the deliberative sentence the adjudged represents the medium hue of many observations, extending over a period of 85 years, and the object is in apparition to us copiously as to be in working sight from months, it constitutes a desirable target [*71] for the Tyro to trim his eye and instrument by, whenever he is bent upon a chromatic onset in that quarter. And as such it carries my recommendation.

So much for ALBIREO, alias β CYGNI

ENDNOTES

[10] Notwithstanding this sombre view, there are rays of hope on the horizon. Already has the Astronomer Royal directed his powerful abilities to the subject-matter; and he has suggested an apparatus for facilitating observations of the of the spectra of stars. This is described in the twenty-third volume of the Astronomical Society’s Notices, pages 188-191.

[11] For the prevalence of red in Sir William Herschel’s star-tints, see the remarks, ante p.15.

[12] Sir Rowland’s scientific bias was developed long before his great and effective POSTAL REFORM; he having been elected into the Astronomical Society in 1822.

[13] Twenty years after the above was is written, my son, discussing β Cygni, says — In magnitude, B is supposedly the slightly variable. In colour, there would seem to be yellow pulsations; at their maximum, converting the simple yellow of A into golden yellow, and the blue of B into greenish blue.

In position and distance these stars present one of the most remarkable instances known of near conformity amongst all ages, countries, and kinds of observers. In position this is partly due to tile large distance, but not altogether; and in distance, the same largeness should tell rather adversely; so that there is in fact only this only explanatory supposition left, if it does explain anything, viz. that, as Professor de Morgan has shown, in his treatise on the Theory of Probabilities, that there must be occasionally amongst men lucky individuals; so amongst the double stars, there may be found here and there a happy pair, where no one can well avoid making a good observation.

[14] See the Cycle of Celestial Object, page 182; and the Speculum Hartwellian, pages 236-238.



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