That worked quite well within Destroyer Command (or was it SH2?), where the flak gun used to have a vertical graded reticule (to calculate firing range, I suppose).

However, I think I´ll stick to Vanjast method: a reticule stuck to the game stopwatch, adapted to the current distances from Polaris to the horizon at every degree from the ecuator to 60N & 60S. Will take some time, though, but well get 1/2 degree accuracy easily. I´ve tried a couple of dead reckonings from the mid atlantic to my hometown in the north coast of Spain, half speed and x512 time compression, and I arrived only 20km east of the desired position. I didn´t use the sextant for that (I hadn´t started it by then), nor made sunrise observations. Luckily, there´s no drift simulated in SH. Afaik...:)

how's work progress? :)