The lowest 16 segments of the primary were removed prior to the SAC being taken down & a huge canvas sail was lashed to the structure above each of the 6 corners of the array.
With nothing much left to catch from above, the cover had to go to allow mirror work (cleaning, re-coating & edge sensor tests) to continue.
Peter & Jono put on an impressive display of extreme cherry-picker piloting as they applied themselves to the task of removing the temporary cover.
Ropes were attached to each corner, looped over a hook on the dome crane & anchored by people on the dome floor.
The high flyers then zipped from corner to corner, undoing the ropes attaching the cover to the structure before each corner could be hauled up to the hook.
With all the corners of the cover securely attached to the hook, the dome crane lifted the whole lot & scooched it away. Great job everyone - what a cool way to spend a morning!
Other than the daily post-dinner pool duel (which tonight ended badly for Management), the next dose of excitement occurred much later while tinkering with the M4/M5 test setup. Running the wavefront camera all the way through focus while the photographer blasts away at 5 frames per second with a digital SLR qualifies as the most fun experienced in the clean room to date.
There was also a breakthrough in our wavefront measurements tonight... By first shifting the pinhole axially & re-focusing the wavefront camera, we could knock out most of the spherical aberration. This made life easier for the spot-fitting routine, allowing us to get stable results with the SAC tilted over a range of 0 to 44 degrees for the first time. This kind of optical stability's really encouraging!