Improving the focus of Las Cumbres Observatory’s 1-meter telescopes

In Las Cumbres Observatory’s global network, the 1-meter telescopes are in greatest demand. Beginning in 2019, we undertook an investigation into the focus stability of these telescopes. We also refined the procedures for setting and maintaining optimal focus. The investigation showed the sensitivity of the telescopes’ optical components to temperature variations. The temperatures within the domes, as well as along the telescopes, are rarely stable for the first 80-120 minutes of science observations. A consequence is that start-of-night focus corrections must later be countered by additional corrections after thermalization. We report the various improvements to telescope focus that our investigation has spawned. The start-of-night focus corrections are now made immediately before science observations begin. Focus checks are now monitored during the night and trigger actionable alerts if they fail. Finally, we report on our effort to use the guide cameras as real-time focus sensors.