The method I mentioned, using the moment when red light turns off as your SR time, seems to work well.
Just know your latitude as precise as possible. From Van's SR/SS almanac get the current local SR time by interpolating between the next bigger and next smaller given lat.value there.
Then just wait for the exact red-light-off-moment (minute wise) and get the difference from the above calculated SR time. This time difference is needed in hours, for example are 75 minutes of time difference to be used as 1.25 hours.
Multiply that number by 15 and that are the degrees your off from Greenwich.
I worked myself from the coast of Northern Africa up to Scotland and from there back to St.Nazaire with very good results of position calculations.
Had no ship encounter on the hole patrol though, nearly ran out of fuel before returning to base
