To the human eye, most celestial objects appear mostly colorless against the darkness of the surrounding space. Occasionally, one can discern hints of color on bright objects like Betelgeuse or Sirius, or the planets seen with the aid of telescopes. Deep sky objects, like nebulae or galaxies, are perceived as having little to no color because at low light intensities, our eyes lose sensitivity to color long before they lose sensitivity to light.
Until the mid-20th century, most of what we knew about the color of diffuse objects was determined by comparing black-and-white photographs made alternately on red- and blue-sensitive plates (for example, the The National Geographic Society - Palomar Sky Survey plates). But this evidence was insufficient for astronomers to build consensus on how color photographs of nebulae would appear. The unprecedented images reproduced in this digital exhibit were not possible before the invention of Super Anscochrome, in its day an ultrafast color photographic film, and the ingenuity of photographic engineer William C. Miller, who spent almost three years developing techniques to optimally combine the new film with two of the most powerful telescopes at the time: the 200-inch Hale and the Samuel Oschin Telescope (then the 48-inch Schmidt) at Palomar.
Humans connect with scenes much more viscerally and tangibly when color information is available. William Miller transformed human connection to the deep sky by photographs and methods that allowed the rest of us to appreciate the beauty of astronomical imagery separately from and in addition to its scientific utility. This digital exhibit presents 16 of Miller's pioneering color astrophotographs taken between 1958 and 1965, many of which were published and became iconic, even inspirational, to scientists, astronomy enthusiasts, educators, and the public in the mid-20th century. A few images of Miller himself are interspersed among the astrophotographs.
William C. Miller, a UCLA graduate, was an optical engineer who designed optical instruments and, during World War II, periscopes and bombsights. For about 15 years he had also been a “volunteer observer” on Mount Wilson until he was officially hired by Mt. Wilson and Palomar Observatories in 1948 or 1949 as a research photographer. By 1951, he was teaching photography courses at Caltech.
Miller spent two to three years testing and optimizing color emulsion film for its use with telescopes. He chose the Super Anscochrome reversal (i.e., positive) film by Ansco, an American affiliate of the German company Agfa. Super Anscochrome was relatively easy to process on site as opposed to Kodachrome, which had been available for years but required factory processing and several weeks of turnaround time. Super Anscochrome had a camera speed of 100 ASA for 0.01-second exposures. However, the film behaved differently when exposed to low light-levels for extended periods of time, with its speed falling to 7 ASA for 4-hour exposure—this apparent loss of sensitivity is technically known as reciprocity law failure. Moreover, reciprocity failure affects each of the three emulsion layers (red, green, and blue) differently. Not only does the film as a whole lose speed, but the color balance and contrast of the film is degraded because some colors are recorded more effectively than others. The most difficult part of Miller’s work was making the arduous tests beforehand to find out precisely how color films would react to long, three- and four-hour exposures needed in astronomical photography. Lab tests, in partnership with Ansco engineers, were critical so that Miller would not waste invaluable telescope time. At first, Miller’s color-balancing was done in post-processing—his technique involved making a copy of the original “raw” film through color filters. Eventually, he streamlined the process and obtained better results by predetermining the necessary color correction and exposing through color filters directly at the telescope.
Miller’s color photographs, at the time unparalleled, made headlines in popular science and news publications in the spring of 1959. They were soon sold by the Caltech Bookstore via mail order in print, slide, and transparency formats.
Miller had no formal training in astronomical photography, yet he originated or refined many of the photographic techniques used by large professional observatories including the development of hyper-sensitizing—a process that baked an immersion of photographic emulsions in forming gas to make them more sensitive to low levels of light. A meticulous researcher, Miller started routine testing of incoming emulsions, and kept a useful database on which emulsions were best for specific uses (clean background, low or high contrast, speed, etc.). Moreover, he acted as the astronomers’ representative in their custom requests to Eastman Kodak Company. Besides his unprecedented success at using conventional color film for long exposure deep-sky photography, Miller contributed with POSSI plate quality control and was a founder for the Working Group of Photographic Materials and the AAS Photo Bulletin. He did not publish many scientific articles–his observatory duties took much of his time. Instead he generously shared his knowledge in meetings or through private communication. Unfortunately, in later years Miller lamented that colleagues did not extend the acknowledgement he felt he deserved for his contributions to astronomy.
William Miller retired from observatory work in 1975. Parallel to astrophotography, Miller cultivated a deep interest in Native American archaeology. Over the summers he led archaeological expeditions in conjunction with the Museum of Northern Arizona (MNA). He surveyed and recorded all the prehistoric ruins he could find in Northern Arizona and Southern Utah over more than 40 years of exploration. His extensive collection of correspondence, maps, manuscripts, photographs, and slides related to Native American archaeology resides at the MNA. Of particular fame are the discoveries of two archaeological rock art sites, which Miller speculated could be representations of the A.D. 1054 Crab supernova—an interpretation also attached (but unproven at best) to several other Southwestern rock art sites discovered since.
Miller‘s groundbreaking work inspired new generations of astrophotographers to continue developing techniques for astronomical color imaging on photographic film, and later with electronic detectors (CCDs). For the next several decades, scientists and nonscientists alike have grown accustomed to seeing the universe in striking color and exquisite detail, particularly with the advent of space telescopes. Natural and false color images of the cosmos are not only immensely attractive, but also of vast scientific value.
A. Mejía and A. Boden.
The deep-sky imagery in this digital exhibit come from digital scans of old photographic prints and slides sold by the Caltech Bookstore between the 1960s and 80s. Some of them have been rebalanced to compensate for fading of the prints over the years, and to best match contemporary publications (magazines and postcards) which aged differently. Unfortunately we do not know whether the original Miller color films survive to this day.
Several of the photographs of William Miller featured here were taken by Life Magazine photographer J.R. Eyerman in preparation for the 27 April 1959 article. Of dozens of photos of Miller at Palomar (now available through Google images) only two were published with the article.
We extend our gratitude to astrophographer David Malin (formerly at the Anglo-Australian Observatory) for graciously providing images and insight on various aspects of this exhibit; and to Susan Sherwood, Executive Director of the Center for Technology & Innovation (Binghamton, NY) for sharing relevant Ansco information and sending a copy of the Ansconian 1961 article.
