Walter Cronkite realized a dream Monday by conducting a symphony orchestra at Carnegie Hall. Cronkite was invited by New York Pops director Skitch Henderson to take part in the Pops' eighth annual gala by conducting the orchestra in Josef Strauss's "Radetzky March," a perennial feature of the Vienna Philharmonic's New Year's Day concert for which Cronkite is TV narrator. The former CBS anchorman wielded a vigorous baton and encouraged the audience to clap in rhythm to the march, just as the Viennese do. Cronkite thanked Henderson for the opportunity of "doing something I've wanted to do for a long time - and in this great hall in its centennial year."