Juvat ire jugis qua nulla priorum Castaliam molli devertitur orbita clivo

Jupsat Pro Astronomy Software

Secrets of the Deep Sky

Get Instant Access

The lines are from Virgil, and freely translated read as follows: "Joyous it is to cross mountain ridges where there are no wheels ruts of earlier comers, and follow the gentle slope to Castalia."

Niepce-Daguerre and Talbot had indeed walked along roads where no wheels before had gone, using entirely different methods. To Talbot belongs the distinction of being the first person to publish a workable photographic system which could be adopted worldwide.

One of Talbot's early photographs is reproduced in Figure 54. Figure 55 shows an exquisite engraving by Talbot of lace - it reveals the most extraordinary detail. Talbot had patented a method of etching steel plates from which prints could be made with permanent ink, in 1852. The engraving seen in Figure 55 is dated 1853.

In his book entitled The History of Photography, author Beaumont Newhall describes the process: "[Talbot] first coated the plates with gelatine to which had been added potassium bichromate. On these sensitized plates he put an object - a blade of grass or a stalk of wheat [or a piece of lace] - and exposed it to light. All the areas except those shaded by the object where made insoluble by light action. Talbot then washed the plate, and the image was revealed in the bare metal, which he then etched." Talbot improved his technique in 1858 - this process, known as photoglyphic engraving, became the basic principle employed in the graphic arts process of photogravure.

In the early days of photography, exposure times were extremely long: Niépce's famous image ca. 1826, near Chalon-sur-Saône, was secured over a period spanning several hours. In 1839, the average exposure time for a Daguerreotype in bright weather could range between fifteen and thirty minutes. In 1841, portraits would typically require an exposure of between one to two minutes; a person being photographed would have to remain very still; in the early epochs of portraiture, children could easily appear out of focus.

In 1851, studio portraits using wet glass negatives required exposures ranging from forty seconds to two minutes. According to photo-historians Helmut and Alison Gernsheim, it was only in 1900 that exposure times of 1/250th of a second became possible using gelatine emulsions. Tell-tale signs of long exposures are evident upon careful inspection of some images, such as in Figure 56.

Warren de la Rue (1862) and Lewis Rutherfurd (1874). The albumen printing method had been invented only in 1850, by Louis Désiré Blanquart-Evrard, and was the first commercially exploitable method of producing a print on a paper base from a negative. It used the albumen found in egg whites to bind the photographic chemicals to the paper. The process is intriguing: A piece of paper is coated with an emulsion of egg white (albumen) and table salt. The albumen seals the paper and creates a slightly glossy surface. The paper is then dipped in a solution of silver nitrate and water, making the paper sensitive to light. The paper is dried in total darkness and is then placed in a frame under a glass negative which is exposed to direct sunlight until the image achieves the proper level of darkness. Albumen prints are placed in direct contact with the negative. The albumen print is therefore a printed rather than a developed photograph, because the image emerges as a direct result of exposure to light, without the aid of a developing solution.

An outstanding collection of early albumen silver prints were recently on display at the National Gallery in Canberra. The exhibit included Julia Margaret Cameron's "English Flowers" (1873), Augustine Dyer's "Narrative of the Expedition of the Australian Squadron to New Guinea" (1885), J.W. Lindt's "Portrait of an Aboriginal Woman" (1873-1874) and his "Studio Portrait of a Miner" (1872). The details in these albumen prints are exquisite; the tones often soft; the feelings invoked in the eye of the beholder, very deep. Albumen prints from egg whites became the dominant form of photographic positives from 1855 to the turn of the twentieth century, with a peak in the period 1860-90 (Figures 57 and 58).

Although some successful photographic images of the Moon had already been shown in public exhibitions - such as the 1851 Daguerreotype by John Adams Whipple, or photographs on paper by Warren de la Rue, Henry Draper, and Lewis Rutherfurd - they had not been made readily accessible. The year 1865 saw the invention of a mechanical printing process known as the Woodburytype (after W.B. Woodbury), which allowed for the placing of photographs in the illustrations of books. The basis of the Woodburytype is essentially an image on a carbon tissue, which consists of different thicknesses of gelatin.

The Dawning 117

This was hardened and then dried before being put in a press with a lead sheet, to produce a matching indentation in the lead. This lead plate is then inked with a pigmented gelatin, which is next printed onto paper to yield the image. Approximately one hundred images could be printed from a lead plate. One of the first books to be illustrated using the Wood-burytype method with its carbon-based inks was entitled The Moon: Considered as a Planet, a World, and a Satellite by Nasmyth and Carpenter, published in London in 1874. Nasmyth produced twenty-four photographs consciously designed for publication in this innovative medium.

Prior to the dawn of the photographic era, seeing was the only source of knowledge available to the Victorian enquirer. The volume by Nasmyth and Carpenter was one of the first books which allowed for the placing of photographs to serve as a "reliable" record of Nature. A pair of photographs entitled "Back of Hand & Wrinkled Apple" is reproduced in Figure 59, while Figure 60 - bearing the title of "Full Moon" - is a Woodburytype photograph secured by Warren De la Rue and Joseph Beck. Of great interest is that the famous lunar photographs by Nasmyth and Carpenter (three ofwhich are seen in Figures 61-63) are actually photographs of small plaster models of the Moon. These photographs served as very early attempts to present vivid three-dimensional relief to readers.

At this juncture, it is important to recall the seminal photographic work of the amateur astronomer Andrew Ainslie Common. He was born in Newcastle, England, on 7th August 1841. His photographs of the Great Nebula in Orion, secured in 1883, are legendary - a work for which he was awarded the Gold Medal of the Royal Astronomical Society in 1884. Mr. Common secured a number of photographs of the Orion Nebula; the effect of increasing exposure times was immediately obvious. Longer exposures would reveal more details as a greater number of photons were allowed to strike the photographic plate; his very short exposure - of six minutes - shows the famous "Trapezium." Inspection of that 1883 plate shows a cluster of four bright stars, at the heart of the Orion Nebula. Increasing the exposure time to only ten minutes shows a dramatic increase in overall detail, including the pres-

Shrouds of the Night

120 Figure 60 [412]

Mr. Common (later Dr. Common) was elected a Fellow of the Royal Society in 1885 and received an honorary LL.D. from the University of St. Andrews in 1891. The potential of using photography in astronomy was ringing a bell whose tones were loud and clear. A.A. Common was exceptionally gifted in the making of mirrors used in telescopes, such as the mirror housed in the Reynolds telescope erected in Canberra, Australia (we shall discuss the pivotal role of that telescope presently). It was A.A. Common who designed a telescope which, as we shall see later, became known as the Crossley reflector: its role in photographically surveying the heavens from the Lick Observatory in California is forever etched in history.

Photographic surveys of the heavens came into general use in about 1890. The year 1893 saw the dawning of a photographic masterpiece that came from one of the pioneers in early astro-photography, Isaac Roberts. Roberts was born at Groes near Denbigh, Wales on 27th January 1829. He was apprenticed - at the tender age of fourteen - to a builder and contractor in Liverpool, and in the years following, became an expert on matters pertaining to building and construction. He founded the building firm of Roberts and Robinson. Roberts' success in business provided a platform of personal wealth from which he could begin to explore his interest in scientific pursuits. Geology was at first his favorite subject, but he also enjoyed areas such as chemistry, microscopy and electricity. In 1878 (aged nearly 50), Roberts, then living at Rock Ferry, Birkenhead in England, acquired a 7-inch Cooke refracting telescope and a serious interest in astronomy began. Roberts was soon captivated by the idea of obtaining a complete photographic record of the skies, and by 1883 he ordered a telescope which was well suited for such purposes, from Sir Howard Grubb. The telescope had a mirror measuring 20 inches in diameter. In 1885, Roberts commenced his work of producing photographic star-charts. After attending a Photographic Convention in Paris at which a scheme for charting the entire heavens was elucidated, Roberts abandoned the idea of producing a complete survey of stars in the northern skies and focused his attention in other domains. It was at this time that astronomers were totally divided as to whether individual galaxies actually existed outside of our Milky Way. Did nebulous appearing objects always lie within the boundaries of our own spiral Galaxy, or were there other "island Universes" - other Milky Ways, each Shrouds of the Night containing billions of stars in their own right? The actual structure of our Universe remained

124 a mystery. Roberts turned his attention to primarily photographing the "nebulae" which were generating such a controversy at the time. In 1888 he retired from business to the summit of Crowborough Hill in Sussex, some 800 feet above sea level and an ideal locale for the erection of his "Starfield Observatory" in 1890 (Figure 64). The 20-inch reflecting telescope was used for photographic work, while the smaller refracting telescope (of 7 inches aperture) was used to visually "track" the exposures as the Earth rotates.

It was at the "Starfield Observatory" that Roberts proceeded to secure many exquisite and detailed photographs of the night sky (Figures 65-71). The images were faint and necessitated lengthy exposures; it required great skill and determination to visually "guide" a telescope for periods of several hours. Roberts employed an assistant, by name W.S. Franks. In 1895, Isaac Roberts was awarded the Gold Medal of the Royal Astronomical Society for his outstanding photographs of star clusters and "nebulae" (many now known to be galaxies). The President of the Royal Astronomical Society, Captain W. de W. Abney, had this to say:

... this year [1895] the eye has to hold a subordinate place, giving way to the photographic plate as a recorder. The latter is a recorder in which there can be no systematic personal error as regards the relative positions of objects which cannot be discounted; and though photography in some particulars does not always speak the truth, yet for a study of the heavens its retina is capable of receiving more accurate impressions than that sensitive surface which lines the eye, and which transmits a message to the brain, more or less tainted with preconceived notions.

Roberts photographed the Great Andromeda Nebula on December 29th 1888, with an exposure time of four hours. This exquisite famous photograph (Figure 65) reveals a brilliant central bright bulge of stars and spiral arms, delineated by young stars and by grains of cosmic dust, curling around the bulge. His photographs received wide acclaim; demand for the images was high. The contribution of Roberts (1829- 1904) is one of the most important collections of early photographs of astronomical objects published, and his work represents a great landmark in both astronomical and photographic history. In an obituary published by the Royal Astronomical Society, we read these words: "He was one of the earliest and most consistent advocates of the merits of the reflector for celestial photography, and lived to see his predilection confirmed in quarters where there had previously been a strong The Dawning prejudice for refractors." A remarkable legacy of Dr Isaac Roberts, Fellow of the Royal Soci- 125

Shrouds of the Night

132 Figure 70 [414]

ety, who started off his career as a young boy of fourteen as an apprentice to a builder, after receiving only a mere elementary education at school.

That a photograph could provide a reliable, truthful and accurate image did not take root immediately. The transition from the eye, which had been trusted for generations, to photographs, was a struggle: as noted above, the President of the Royal Astronomical Society had, in 1885, alluded to this: "though photography in some particulars does not always speak the truth, yet for a study of the heavens its retina is capable of receiving more accurate impressions than that sensitive surface which lines the eye ..." (italics, ours).

There is a most interesting volume by the German astronomer Johann Krieger published in 1898, the Mond-Atlas, which seeks to marry observations of the Moon by eye, with lunar photographs taken in the late nineteenth century. Krieger had secured low resolution photographs of the Moon taken at the Lick and Paris Observatories. He then enlarged these, and added exquisite details on the photographs by hand (using charcoal, ink and graphite pencil). The features which he had added were those faithfully observed by eye over long periods, at his observatory in the Munich suburb of Gern-Nymphenburg. His observatory was equipped with a fine 10.6 inch Zolliger refractor telescope. While earlier attempts at lunar cartography were solely visual, Krieger ingeniously combined both photograph and the eye. In examining some of Krieger's drawings on photographs of the Moon (Figures 72-74), one can almost perceptively experience the tension which prevailed at that time -even in the mind of Talbot, the pendulum would swing from considering photography as a means of "drawing" and of "not-drawing."

In 1874, Tissandier published a book entitled Les merveilles de la photographie in which he formulates the photographic method as being scientific and objective. In the 1876 English translation of Tissandier's book, we read: "It is impossible to avoid a certain emotion in contemplating the negative of a lunar photograph ... it is quite certain that it is mathematically correct, for it is the light from its surface that has winged its flight to our own globe to print

Shrouds of the Night the picture."

Was this article helpful?

0 0
Telescopes Mastery

Telescopes Mastery

Through this ebook, you are going to learn what you will need to know all about the telescopes that can provide a fun and rewarding hobby for you and your family!

Get My Free Ebook

Post a comment