Thanks, Nathaniel that's a very kind offer. I'm looking to use the sextant in SH5 really, so not sure how much or how it differs from real-life techniques.
I will have a play about and come back to you if I need some clarification.
I also just came across this series of videos
https://www.subsim.com/radioroom/sho...d.php?t=246847
have not had time to look at them yet, but they look very good
regards