Now here is the question I would like answered by someone. Besides calculators there are web sites you can use to enter your sextant sights into and hey presto you have a position line. I have never used a specialised Navigation Calculator. So to answer your question I have used a calculator do the practice with, but not used a calculator to find my location on the face of the earth without the back up of the GPS. I am planning another trip a long way from the coast and will be getting back up to speed on the celestial navigation. The books are virtually impossible to get now as the calculators have made them redundant. Unfortunately for me I lent the books to some friends who were sailing up around PNG and I never got them back. The books allow you to find the results of the spherical triangle without any calculations. I managed to get a genuine set of book HO229 (I think the name was) from an American lady (whose husband had passed away) who was selling all the gear form her Junk (sailing boat) which her husband and she had been sailing around the world. I learnt the use of a sextant In Cairns back in 1985 from a guy off a French boat (Francis & Christine (sounds difference in French)) when the calculators were quite expensive. Hello Maxm No worries about the thread jack.