The RTMC Astronomy Expo was one of the major gatherings of amateur astronomers in the United States for five decades, from 1969 to 2019.
Due to low attendance the date was moved back to the Memorial Day weekend in 2011[1] The organization annually presented the Clifford W. Holmes Award for "Major Contribution to Popularizing Astronomy, the Warren Estes Memorial Award for "Best Use of Simple Materials and Technique" in making telescopes, and the Clyde Tombaugh Award "Creative Innovation in Telescope Design".
The Expo promoted family activities with swimming, canoeing, horseback riding, archery, wall climbing.
[2] The RTMC also produced an early autumn star party called Nightfall in Borrego Springs, CA.
Nightfall is still held by the Riverside Astronomical Society on the weekend in October that corresponds with the new moon.