When I was 9 years of age in 1972 my dad got an Ebbco plastic sextant, a Nautical Almanac and went to an evening class to learn this. Exactly why he did this is a bit of a mystery though. I think it was just general curiosity as our boat is in a lake and not in the Atlantic. Tabular data has always had an impression on my nerdier side so I was hooked. In high school I found formulae for the sun’s orbit and programmed my ZX81 and later ZX Spectrum with them.
I remember trying to get fixes by the sun but was always more than a nautical mile away. Recently there was Freiberger Trommelsextant on an auction site and with an artifical horizon, or in the boat, I now get MUCH better fixes, definitely within 1 nautical mile and sometimes even spot on.
So, that’s the what. The why is partly because of a mathematical fascination in the subject and partly to keep the
ancient old methods alive.
The Freiberger’s micrometer was stuck on delivery so it was a nice mechanical challenge to get it going again. I have repaired cameras and shutters as a hobby so I had the tools for that.