Putnam's political and business interests lessened the amount of time he could devote to the Lowell Observatory in the 1930s and 1940s. The Observatory's three senior astronomers—V. M. Slipher, E. C. Slipher and C. O. Lampland—were no longer doing much research or publishing and prevented other, younger astronomers from using the telescopes. Lampland died on December 14, 1951, and Putnam decided to use the occasion to bring in some new blood. Putnam hired Albert Wilson, a Caltech astronomer who had led the Palomar Sky Survey. Although Wilson clashed with Observatory personnel and resigned after only two years on the job, with Putnam's support he greatly modernized the Observatory's procedures, policies, and equipment. Most importantly, he instituted a mandatory retirement age of 70 and resilvered the Observatory's Ritchey–Chrétien telescope (now named the John Hall Telescope). When Wilson came under attack for laying off photoelectric research staff, Putnam publicly reaffirmed his confidence in him.