In another letter to Holden, he urges Holden to consider the capacities of the eye and the advantages of observing the cosmos directly through the telescope, rather than relying secondarily on the images produced by the camera. He writes that the eye can detect more detail than the photographic lens, and argues that there is more detail in his drawings of the moon than the best photographs of the moon.
An oversized set of prints of Trouvelot's drawings (approximately 2' by 3'), two of which are displayed in case 3 and case 4, was gifted to the Lick Observatory by John R. Jarboe in 1887. The set originally consisted of 15 plates, but five have been lost. W.H. Wright, a later director of the Lick, wrote in 1937 that the illustrations "were of little scientific value and were finally relegated to a store room." The remaining prints are accessible through UCSC Special Collections, or they can be viewed online through the digital collections of the New York Public Library. The prints in the above slideshow and found elsewhere on the site are from the digital collections of the NYPL.