Hale's visual refractor of 1891 at Kenwood Observatory was quickly supplemented with an interchangeable Hastings-Brashear objective corrected for photographic work in the blue part of the solar spectrum. (The first "visual" objective, seen here on the right, had been corrected for sharpest focus in yellow-green light.) This image shows the objectives circa 1995 after they had been removed from long-term storage in the Yerkes vault, in preparation for use in a laser guidestar experiment at Apache Point Observatory. Both achromats were found to have been assembled backwards in their cells. Such misassembly is common in the case of the Hastings flint-forward design.
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