JWST's primary mirror consists of 18 individual segments, each of which can be moved on 6 different axes of freedom. This allows the telescope to maintain perfect focus, despite changing temperatures and micrometeorite strikes on its optics. The objective was 150 nanometers of wavefront error, but the current error is down to just 65 nanometers. In early October, engineers measured the telescope's jitter and refocused it again, bringing it to its perfect alignment

The post How Webb Stays in Focus appeared first on Universe Today.