library copies
Failing a purchase try RAF Museum Dept of Research and Information Services aka DORIS. Not only will they have copies back to the year dot but also errata and amendments.
For some excellent formulae still in print is Admiralty Manual of Navigation, the single volume red bible from HMSO if there is such a thing anymore. Disregard any formulae that equate sin 1' with 1' and just use 1' as is! It's a throwback to the days of logarithms and not necessary with modern calculators.
Spherical trigonometry is fun!