The primary mirror for the James Webb Space Telescope (JWST) will consist of 18 separate mirror segments. The optics for the primary is now finally coming together with the mounting of the first mirror segment . Assembly of the full primary will occur over the next year and the curious can watch it come together minute-by-minute on the JWST Webbcams. Those wanting to see faster progress can break out their Benny Hill music[*] and watch JWST Time-Lapse movies.
[*] The tune is actually Yakety Sax.
I thought the units for this mirror was specified in radians.