You mean that he would not have noticed the move until the steamer was well SSW?He would only know for sure if the other vessel had moved if, after taking several bearings together, the bearing changed appreciably and constantly to one side or the other of 180 degrees. He would automatically take several bearings at a time because, although its movement would have been dampened, and the ship was stopped in still, flat calm conditions , such a compass can often be unsteady when the ship is underway or swaying in a wind and or swell.
What is bothering me it is inconsistencies between the testimonies of Mr. Boxhall and Mr. Gibson.
Mr. Boxhall testified that he saw the red most of time. From the testimony of Mr. Gibson we know that Mr. Boxhall could have seen the red only for the last 10-15 minutes before he left the Titanic. Before that he saw red and green together. It will be interesting to find out for how long total Mr. Boxhall was able to see the Californian’s sidelights.