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Updated: May 2, 2025
The telescope used was of eight inches aperture and forty-five focus, its field of view owing to the "portrait-lens" or "doublet" form given to it embracing with fair definition no less than one hundred square degrees. An objective prism eight inches square was attached, and exposures of a few minutes were given to the most sensitive plates that could be procured.
The simpler the background the better. Near-by foliage is not good for figures; it is too confused and the figures will mingle with it. Sometimes the adjustable portrait-lens, which can be slipped over the other, will obviate that trouble by blurring everything not in exact focus, and this lens will allow you to stand nearer the object and so make it larger on the film.
Special conditions were required for success; above all, a wide field and a strong light-grasp, both complied with through the use of a 6-inch portrait-lens. Even thus, the sensitive plate needed some hours to pick out the exceedingly faint stars collected in the galactic clouds.
"In the photographs made with the 6-inch portrait-lens," Professor Barnard wrote, "besides myriads of stars, there are shown, for the first time, the vast and wonderful cloud-forms, with all their remarkable structure of lanes, holes, and black gaps, and sprays of stars. They present to us these forms in all their delicacy and beauty, as no eye or telescope can ever hope to see them."
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