Julian, working out sights was a very tedious task. As Jim said, Pitman started the process soon after the sights were taken. He probably got as far as correcting all the numbers for known corrections such dip, sextant index error, atmospheric refraction, and time adjustments to bring all sights to common time point reference in GMT. That was the easy stuff. Boxhall would have to do the sight reductions, and even with the help of printed tables, as Jim said, it would take a very long time. We know he completed this work before Lightoller left the bridge because he showed the 7:30pm position to Lightoller before going to Capt.Smith's chartroom for Smith to put onto hs chart. I believe Boxhall mentioned seeing Smith last around 9:30 which would have been after Lightoller and Smith had spoken. By the way, Smith was back from his unofficial social obligations before 9. (You can forget about the Daisy Minahan's affidavit where she said she saw Smith leave Widener party between 9:25 and 9:45. . Daisy was in bed by 9:30 according to her sister-in-law Lillian Minahan who left the part the same time that Daisy and her brother did.) What I find interesting, however, is that 1/O Murdoch allowed Boxhall to work on sights for compass deviation error instead of having him stand watch out on the bridge, given that he expected to be up to the ice at any moment. Perhaps, Murdoch was bit overly confident in his own ability to spot ice in time to avoid and decided he did not need an extra pair of eyes out on the bridge with him.