Admiral William Henry Smyth (1788-1865) was a gentleman amateur astronomer who was born in the same year when Captain Arthur Phillip was founding the Australian colony of New South Wales under the British Crown. Although born in Westminster, England, his family originated from the American state of Virginia. Smyth at a young age joined the Royal Navy and by the age of twenty-nine (1817) he was made Captain. His commission started after being posted on the ship H.M.S. Adventure whose voyage was to make an improved survey and suitable nautical chart of the south-eastern and central Mediterranean that included all of Italy and Sicily. This ship had carried all the necessary astronomical equipment to do positional observations.
The survey also gave Captain Smyth the opportunity to explore the cosmopolitan cultures around the Mediterranean during the times of the Napoleonic wars. Early in Naples during 1815 he had met and married Annarella Warington who was to be eventually involved as an assistant to his latter written works including the most well known book, the “Cycle of Celestial Objects” or ‘Cycle’. Although his training was involved in astronomical positioning, his interest in amateur astronomy was likely sparked in 1817 by the Sicilian astronomer Giavanni Piazzi while visiting his observatory at Palermo in northern Sicily. After 1825, he receded from his more active naval duties, but remained a British Naval Officer. He later achieved the rank of Admiral in 1863 just prior to his true retirement at the age of seventy-seven.
Smyth had become far more serious about astronomy after about 1825 when he moved one hundred kilometres north of London to the small town of Bedford. Here he started his first series of astronomical observations from his private observatory - producing the now renown Bedford Catalogue. In 1839, this observatory was dismantled and removed to Cardiff. The main telescope was then sold to Dr. Lee and re-erected at the Hartwell House and placed in a new observatory designed by Admiral Smyth. Smyth did on occasions still used this instrument, as his residence at St. John’s Lodge was not too far away. After settling in, he again produced a new series of visual astronomical observations between 1839 to 1859.
One of his sons, Charles Piazzi Smyth also became astronomer and artist. Charles spent his early years at the Cape of Good Hope between 1835 and 1845, and then return to Scotland as the Astronomer-Royal. (“Charles Piazzi Smyth, astronomer-artist: his Cape years 1835-1845.” Cape Town (1983) by the southern astronomical historian Brian Warner.) Charles Smyth had strongly influenced his father regarding his stellar colour experiments that culminated with his father’s last major work - the “Sidereal Chromatics.” It is likely the influence extended from his own point of view, his artistic talents, and his much broader astronomical knowledge and experience.
Admiral Smyth later became President of the Royal Astronomical Society in 1849-50 and did contribute various papers on diverse subjects that appeared in several Journals between the years 1829 and 1849. Observationally, his principal telescope was a Tully 5.9-inch refractor at his home at “Hartwell” in Bedford. The telescope itself was sold to his friend, Dr. John Lee - the same person the initial that the letter used in the introduction was recorded in the beginning of the “Chromatics” and we still know it was still in use by him sometime after 1865.
Admiral Smyth eventually died in the evening in September 1863 at his home in Cardiff at the age of 78 years old.
One of his most best known of his astronomical works was the “The Cycle of Celestial Objects ” published in two large volumes in 1844. This particular work was awarded by the Royal Astronomical Society with its prodigious Gold Medal. These well researched volumes proved very popular among amateur observers, that were again republished in 1986 by Willman-Bell as the “The Bedford Catalogue” formatted as seen in the original 1844 edition. There are still available as a single book. This tome is the modern-day originator of many of the observational texts on the general appearance of deep-sky objects and double stars seen through small to moderate apertures.
Various biographies about Admiral Smyth do exist. Some of these are on the I#nternet are worthy reading for those interested in more about the man. Ie.
Admiral W.H. Smyth’s four main astronomical works include;
A Cycle Of Celestial Objects [n 1844]
Aedes Hartwellianae [La-1851]
Speculum Hartiwellianum [La-1860]
Sidereal Chromatics [n 1864]
One of the first significant astronomical documents on the colours of double stars was “Sidereal Chromatics: Colours of Multiple Stars”, often just now named the “Sidereal Chromatics”. Written in 1864, almost a year before his death, this interesting work was based on several false premises - centred mainly on the nature and velocity of light through space and the true origins of colour. This means that much of the scientific background was both misplaced or just simply wrong. However, in essence it is an obvious development of Admiral Smyth’s astronomical works and his voyage of exploration regarding the visual double stars observations of colours. One of his interesting methodologies employ in the paper was the demonstrative rough “colour blind-tests” on double stars, which included several noted double star observers, amateurs astronomers, but also of Smyth’s associates and friends - and even their wives.
In the scheme of things, much of the text has now been placed as only of a casual interest, but it does contain some very interesting discussions and ideas on the visual interpretation of the nature of double and multiple star colours. During the years after this tome, several other papers have been published on double star colours in the literature. These latter papers were eventually replaced in the early part of the 20th Century with the advent of photometry and colour measurements like the B-V colour scale. This latter measure soon produced the first colour-magnitude diagrams of the open star clusters - leaving a toe-hold into stellar evolution theory. After this time serious visual observations of colour immediately became obsolete.
His interest in the colour of double stars and astronomy culminated with the Sidereal Chromatics, some of which appears in a more rudimentary form of the “Bedford Cycle of Celestial Objects” first published in 1844, followed by the “Aedes Hartwellianae” in 1851 and the “Speculum Hartwellianum” or “Hartwell Cycle” in 1860. When “Speculum Hartwellianum” was originally published in early 1860, it caused some reaction from the astronomical community.
One such response was by S.M. Drach as an “Letter to the Editor” on the 12th March 1860 (M.N.R.A.S., 251 (1860)). This letter discusses an observational device called the Saussure’s Cyanometer which uses a colour card attached to a binocular eyepiece. This presumably would eradicate the need for;
“...the conflicting opinions of simultaneous observers on the same night of double stars... ”
After Admiral Smyth’s death, Sidney B. Kincaid in the next year (1866) published on abstract “On the Estimations of Star Colours”, M.N.R.A.S., 27, 264-266 (1866) on the question the possibility of variable coloured stars. He concluded regarding 95 Herculis, that;
“...no crucial example of the change in colour of a star has been determined ; although there is every reason to believe that such objects vary as well in their hues as in their apparent brilliancies. ”
Modern solutions for single and double stars and their evolution can be traced back to the works created in Smyth’s day. The immediate significance of double stars was first derived by Sir William Herschel. His initial observations of pairs was to find their numbers, true gravitational connection and comparative motions. Yet the understanding behaviour and origin of light became also a significant hurdle. Prior to Einstein’s Special Theory of Relativity, science thought that different wavelengths of coloured light produced by the stars were primarily caused by the varations in the speed of light.
This was based on the 1842 assumption of Christian Doppler (1803-1853) who explained the colour changes of variable stars being caused by their relative motion towards or away the Earth. Stars therefore moving towards the Earth would be bluer while those that were receding would become redder. However the failure of this postulate was that the colour beyond the red or blue parts of the spectrum was replaced by other light like infra-red, etc., instead of leaving some predicted blackened or missing part of the visible spectrum. It was Hippolyte Fizeau (1819-1896) who realised the consequence of the red or blue shift did not change the colour of the object but did change the relative positions of the spectral lines depending on how fast and the direction of motion towards or away from the observer.
Secondly, physicists and astronomers also had assumed that light was simply propagated and behaved exactly the same way as ocean waves or ripples on a pond. (See Page [*40]) This assumption meant that some kind of transmission medium was required for the waves to pass through - the now debunked theory of the æther. If so, then the velocity of light would then be variable depending on the medium. Ie. In air or in water. This is true. However what is not true, was that different wavelengths of light travel at differing velocities.
Ideas regarding the differential velocity of light were not new. Initially proposed by Isaac Newton, light was postulated that the cause of certain colours of light travelling at different rates were inherent to the medium itself. Stellar colour production was therefore a problem influenced by the æther - whose composition, which Smyth correctly says; “...we are at present profoundly ignorant.”
Smyth wanted to expanded the debate to include the Fresnel and Young’s “undulating theory” [*41]. These scientists, among numerous others, showed that pure colours are just monochromatic light that had just different wavelengths. If the red waves were shorter compared to the longer blue wavelengths, as Smyth strongly argues, then the blue light must travel faster than the longer wavelength red light. If one were to look a star some distance away, then light from the star meant that the different colours emanating from the star would arrive over a certain time interval - perhaps over several weeks. Furthermore this could be extended to motion of the source. Assuming a Galilean or Newtonian framework, known as classic physics, then the speed of light was direction dependant - such that, we would see different speeds travelling in different directions with respect to a moving observer. This is also not true, and was properly dispelled by James Maxwell (3) in his set of equations that were experimentally proven with the famous Michelson-Morley light experiment in 1887. In all this eliminated the entire need for the carrier background of the æther. Maxwell’s understanding of electromagnetism theory finally proved to be the interconnection between electricity and magnetism - so light becameknown as electro-magnetic waves.
Maxwell then further deducing that all kind of light travelled at similar speed. By 1887 his prediction was vindicated with the detection of radio waves from an electronic circuit and resoundingly confirming the speed of light ‘c’. These ideas were later affirmed by Lorentz in 1900 and by Einstein’s Special Theory of Relativity (1905) - explaining that ‘c’ was an absolute constant. This gave an understanding of both the general behaviour of light and the energy it contains.
In the beginning of the 19th Century little was known about the evolution of stars, but as this century passed by, a growing impetus in the subject saw giant steps towards some understanding. In 1800, the stars were still just considered as part of the celestial realm, whose composition and nature were always going to remain hidden from the World. A main key to the discovery of their chemical natures occurred by studying the light from the stars themselves. In 1802, William Wollaston analysing some starlight by passing it through a narrow slit found that the normal coloured spectrum was crossed by numerous dark lines which were not gaps in the stellar spectra.
It was originally assumed that the stars were made in clouds of gas to from red giants. As the star evolved, gravitational forces crushed the body, so that the body slowly changed through the spectrum to end as a smaller bright blue-coloured body before being extinguished as a white dwarf ember - like the companion to the bright star Sirius. Such evolution seemed natural and necessary - mainly to explain the energy source that made the stars shine so brightly. In the mid-1850’s interest with double stars were mainly in the real hope of either discovering how heavy the stars were, or to sort some evidence of their evolution. The former postulate needed enough evidence for orbital motion, and at the time of Smyth’s writing, only few examples were known. Most prominent of the stars was the southern binary of Alpha Centauri which is discussed in detail on Page [*39]
However, the 19th Century was greatly hindered without the familiar instrumental and telescopic means that exist today.
The first problem in stellar evolution theory is to understand what actually makes the stars shine. In the earliest of times, stars were once commonly thought to be unchanging and eternal. Later it was generally accepted that all stars were actually shining by either by some combustible fire or by celestial friction against the invisible aether. However, these theories were insupportable because of the aeons that the stars had to have been shining. When coupled with the substantial fossil and geological evidence and a long-term consistency for the solar radiation, it was shown that any a combustible energy source was clearly impossible. Soon some elementary calculations showed that if the Sun were made of coal then its age would be merely 6,000 years!
Herman von Helmholtz in the 1850’s initially proposed the theory that the Sun and stars generated heat by simple contraction. This was conveniently provided by gravity literally squeezing the energy out of the star. Helmholtz proposed that if the Sun shrank by as much as eighty metres per year it would liberate the quantity of energy presently radiated by the Sun. However, if the Sun had shrunk from an infinite size it could only be extended to about fifty million years. This theory remained popular until the 1920’s, but again remained inadequate against observation.
For many years the source of the sun’s and stellar energies remained elusive, with stellar evolutionary theory proposed that red giant stars were younger than hot blue stars. Supported by Sir Arthur Eddington in the 1920’s, this “compression theory” further indicated that stars started as red giants or supergiants and went through the entire spectral sequence to finally transform into a smaller blue star to presumably end as a white dwarf ember. Yet the early spectroscopic analysis showed that this could not be true, as the red stars had too many metallic spectral lines - certainly an identifying precursor of old age.
A belief in this theory still continued until the late 1940’s. For example, in the 1940 general astronomy text, “A Story of Astronomy” by Draper and Lockwood, which states;
“Until fairly recently...it was generally believed that stars simply evolve simply by loss of heat. The extremely hot bluish-white stars were thought to be the young vigorous members of the star family. These stars after losing some of their heat, so the theory said, passed successively through the increasing cooler stages of yellow and orange-red, down finally to the last oldest and coldest age of all, that of the red stars. This particular evolutionary theory, however has fallen by the wayside, as so many attractive theories must. Astronomers know now that the cooler stars are divided into two classes, the giants and the dwarfs, the dwarfs showing much greater densities than the giants. It seems probable today, as a result of research in this field, that the evolution of the average stellar body begins with a red giant star, passing with increasing temperature range through the orange-red, yellow and bluish white which shows the maximum temperature of all. Then it is believed that the star’s temperature begins to decline, passing in reverse order back through the yellow, orange-red and red stages, with a corresponding increase in density as the temperature decreases. The end of this sequence brings us to the dense red dwarf stars, which seem to be the densest and coolest, and probably the oldest of stars. The next stage after the red dwarf is perhaps oblivion - so far, at least, as any very active radiation is concerned.”
Until Einstein’s “energy-mass equivalence” - E = mc2, where matter can be converted to energy by nuclear fusion, or vice-versa, but this concept of red to blue evolution of stars remained fixed as the best theory. Some old texts can be seen to elaborate Helmholtz’ theory. Today some views of these theories can be enjoyed with some amusement.
Smyth in the Sidereal Chromatics argues that all stars should be pure white with the stellar light being a blend of all the colours arriving at different rates. Otherwise, the only other possibility becomes that all stars could be varying significantly in colour - which he used the examples of the colour changes seen in the decreasing brightness of the Tycho supernova seen 1572. It might be also the cause of the presumed change in the colour from ancient times of the brightest star Sirius, R Geminorum [*19], [*20] or the eclipsing variable star Algol (β Persei). Although there appears that these stars do have significant changes in brightness, Smyth goes on to further argue that some changes in variable stars could be explained by his stellar colour theory. (4)
It is interesting why the astronomers of the day, then described as natural philosophers, persisted with this view. It could be equally argued that the colour differences were actually caused by stellar surface temperature or another is the various stellar radial velocities. This presumed colour variability could also be caused by physical changes in the stars themselves - the classic example being the Cepheids, who may change by a spectral class or two during the periodic cycle. Ie. G to K.
These changes in colour made Admiral Smyth think that this was something that was assumably detectable if the human eye was properly trained. Although he then goes on to correctly identify the primary sources of errors; being namely the atmosphere; the star’s altitude above the horizon; the effects on the eye by artificial light sources; and problems with achromaticity of the eyepiece - yet surprisingly completely dismisses this serious known problem with refractors, stating “... [it] will not affect the difference observed! ”
A most innovative idea in this text was to use of a standard colour chart at the eyepiece for observational colour determination. page [*48], and idea I have toyed with myself over the years. In the years before Smyth’s examination of star colours, some had proposed the use of coloured jewel-stones and gems as comparisons. Often these were not used - mainly because of their poor range of colour and being too costly to acquire for practicable use. Smyth also proposed the use of water colours placed on white card. These he suggests could be made up by any “chromatic” observer as required, using either paints or various inorganic chemicals. Problems with using standardised colour charts is the illumination to view the colour chart itself - and is still a problem. Today, we can control the illumination readily, but during Smyth’s day the use of candle light or “lamplight” means that the illumination produced a yellowish hue or tint. Smyth eliminated this effect by assuming that these “yellow” stars were colourless but could be separated by some “greyness scale.” Ie. Origin of the grey stars. He summarised the nature of colours under “lamplight” as;
“The very numerous shades from white to pale yellow are so 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.” [*54] and [*55]
The existence of colour has been known since the dawn of time and has been exploited by both the animal kingdom and humankind ever since. All of the early human civilisations have taken colour essentially as matter-of-fact and it wasn’t until investigation of the optical properties of materials that any scientific progression occurred. One of the earliest attempts was with Isaac Newton who first investigated the breaking up of white-light into the colours of the rainbow. It was Newton’s rainbow colour circle that became the first scientific division of the colours. These seven colours being violet, blue, green, yellow, orange, red, and indigo.
It has been known and demonstrated from the times of the earliest painters that the use of three basic colour pigments combined with black and white could be used to produce the infinite varieties of hues. Artists used chemical materials or substances, properly called chromatic pigments, but are now now known not actually be related to the properties of monochromatic light. These painters saw that the primary colours were red, yellow and blue, and were deemed absolute colours because they could not be produced by any other means.
Regarding the radiation of light, it was Thomas Young in 1807 who stated these absolute colours were quite different. He stated that the primary radiations of the spectrum were red-orange, green and blue-violet. Differences between the painter and the physicist were soon to be brought to some understanding regarding these coloured pigments and light. These we now know as the additive colours and subtractive colours, and some thing incidentally that was taught to us at a very young age when we all first went to primary school. Consequently, an example of additive colours, is when the Young colours are added together to produce pure white light. If pigments of the artistic colours are added together, these produce pure black or subtractive colours.
These differences of these colour combinations were first explained correctly by Hermann von Helmholtz in 1855. Later the usefulness of these effects was exploited in both photography and in commercial printing. Similar principles also work with colour computer monitors and in colour televisions. In painting and art most colours are usually recognised as achromatic or neutral colours, but whether white or black are really “colours” is still open to some debate. Optically, white light is not in reality defined as colour because it comprises as a sum of all the radiations in the visible spectrum. With optical light, including sunlight or starlight, there are no mixtures of black and white. What we are describing in this instance is a montage or blend of monochromatic colour hues. This is far different from the artistic views of the colours seen on Earth. It is important to note that in the physical world cannot be truly or adequately described in the artistic world - therein the major fault with our early ideas about colour. (Actually since about the mid-1850’s)
As such, in observational astronomy there is no need, therefore, to describe colour sensation and sensitivities in terms of tone, value or purity - or even in “lightness” (or greyness). These are adequately described in the simpler terms of hue and saturation.
In most terms, saturation is often used in terms of an absolute purity of colour, but this really is an abstract hypothesis. In reality such light finds saturation not as a ray of a determined wavelength but a mixture of radiations of differing proportions, often signified by a specific wavelength that predominates all the others.
In nature, all colour observed is based on the colour of the light source, the absorption of light by the chemical composition in the object, and the re-emission of the non-absorbed light. Most stars are in fact mainly “unsaturated” due to difficulties seeing colour by our eyes against the dark background sky.
[3] James Maxwell also did an investigation on the physical behaviour of light. He formulated the commonly used educational science experiment by combining red, blue and green light to make white light, and demonstrated how the colour vision in the eye worked in principle. In comment, the sad things about all these deliberations that occured around at the same time as Smyth’s, was that he never saw these releations.
[4] Smyth states that the french atronomer Arago tried seeing such color changes without success. This prompts the consideration that observers before Smyth had thought similar ideas - which failed because observations could not be made to prove or disprove a general theory.
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