I was under the impression that the compass checks were mandated to take place every half an hour?
If that is not the case I may have miss understood a discussion in a different thread.
No, Rob, you did not misunderstand. There was a very sound reason for the Compass check intervals
The Compass checks would not be made at the time of a Watch changeover Too much to do at and just before and after that time.
There would have been one at 11-45 am before Noon and 30 minutes thereafter. It follows that if there was no planned clock change, then there would be a check due at 11-45 pm. This means that when the Watch was handed over, the latest compass check was only 15 minutes old.
This held good for the Senior as well as the Junior Watchkeepers. Thus when Lightoller handed over to Murdoch the Compass error on the Course Board was the very latest version.
However, if the clocks were to be set back 24 minutes at midnight and the compass error had been determined at 11-45 pm unaltered time, then when Pitman relived Boxhall in the normal way, the compass error would already have been ancient history and contrary to intentions. i.e instead of being no more than 30 minutes old, it would have been 39 minutes old.
11-45 pm...compass check.
add
15 minutes.
Midnight (1) - subtract 24 minute
Time 11-36.
add
24 minutes.
Midnight (2) -Watch changeover.
Interval since compass check = 15 + 24 =
39 minutes.
However, if there
had been such a clock change, then when the 3 bells were heard at or near to 11-40 pm the compass error check was due in 5 minutes and Boxhall was on his way to relieve Moody so that the latter could go to the Compass platform and take a star azimuth. Moody could do so with confidence since QM Olliver had made sure the lights on the compass binnacle were in good order for the task. However, events changed the good intentions.
Just saying