Hello Mila.Sam, If the Titanic's course was 266°T, should not have Mr. Groves be able to observe almost the whole length of her?
I am sure that Sam will answer this himself in due course. However, you are correct. If a vessel like Titanic was approaching the Californian as described, her starboard side would be very clearly visible as a blaze of light, a considerable time before the former stopped.
There has been a great deal of unconsidered nonsense written about this part of the Titanic story. Consider the following facts:
If both Californian and the Titanic turned exactly at The Corner as planned and had maintained their planned courses, then when the latter was in the direction of SE from Californian, stopped at 42 North, 50-07'West, they would be about 17 miles apart and Titanic would have steamed 127.5 miles in a time of 5 hours 50 minutes (no clock alteration) and a total of 251.5 miles from Noon that day. This would have given Titanic an average speed of 21.86 Knots from 5-50 pm and an average speed from Noon of 21.3 knots.
Additionally, if she was making 22.5 knots just before she hit the berg, as indicated by the Patent Log reading, then 30 minutes before she stopped, Titanic would have been over 25 miles from the stopped Californian. and invisible from the latter.
However, It has been stated that Californian stopped at 42-02'North, about 3 miles farther south from where her captain said she stopped and 2 miles north of the above example. That being the case and if Titanic did turn at The Corner as planned, then the separation distance between the two vessels when stopped would have been close to 20 miles and 30 minutes before that, nearer to 28 miles.
No way did Groves or Lord see Titanic's lights 30 minutes before she stopped.
Furthermore; if those on Californian could see the lights of Titanic, then Fleet, Lee and Murdoch would most certainly have seen Californian's lights Murdoch's eye were 20 feet higher that those of Lord and Groves and the latter had the help of binoculars.