Reading Nature, Observing Science: Examining Material Practices in the Lick Observatory Archives and Kenneth S. Norris Papers

Transcription of Perrine's copybook, circa 1890s

The exposure necessary to bring out the structure of faint nebulae are very long, often of three and four hours duration and for some special objects, ten or twelve hours. These long exposures are attended with difficulties, many of which would disappear if the necessary light action could be secured in one or two hours...the negatives secured with shorter exposure would be of greater excellence and would show structure that is now lost to thinning due to difficulties of guiding [the telescope] during very long exposures.

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