NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Practical Calculators for Navigation
From: Wendel Brunner
Date: 2026 Jul 4, 09:23 -0700
From: Wendel Brunner
Date: 2026 Jul 4, 09:23 -0700
Luc Desmedt asked last April if people had thoughts on practical calculators for navigation. I have thought about that quite a bit, and starting in the 90’s programmed several calculators for use at sea or land to solve navigation problems.
I think the most straightforward approach is to use a simple, non-programmable scientific calculator. I use a Casio fx-300MS; it has 8 user-programmable memories, a simple degrees - minutes - seconds key to enter angles and time, legible screen, long battery life and you can get it on Amazon for about $15. With that calculator you can eschew all tables and easily calculate the HC and Azmuth solutions for your sights from any convenient assumed position, including your dead reckoning position, using the declination and GHA of the body taken from the Nautical Almanac. If you want to skip the Nautical almanac as well as the tables, in The Calculator Afloat, Shufeldt and Newcomer describe a simple way to calculate the GHA and declination of the sun for any date and time during a year using two parameters specific to that calendar year. They tabulated values for those parameters for the years 1979 through 1999. In a post to the Nav List in April 2025, I updated that method and included the values of the parameters for the years 2025 through 2045. The results are accurate to within 0.2’ - 0.3’ or better - plenty good enough for small boat work. These calculations are also quite practical on the Casio fx-300MS, where the user memories come in handy. So with this $15 calculator and two parameters for the year, you can easily work up sun sights anywhere.
There are formulas in the NA for correcting sextant measurements for refraction and dip and calculating the intersection of LOP’s. It would be nice to enter these and perhaps a few other small programs into a simple calculator, along with programs to solve the Nautical Triangle and calculate the GHA and declination of the sun. In the 90’s I used a Casio fx-4500p with 1000 programmable steps capacity, but these calculators are no longer available. The Casio fx-3650p that Luc suggests has only 390 steps, and I am not sure it is still available either. You could use one of the powerful graphic calculators like the Casio fx-9860GII and try to ignore all the graphic, statistical, matrix, calculus functions, etc. and just write some simple programs, but they don’t make that easy.
If you want to add ephemeris other than the simple algorithm for the sun, like for the moon, planets and stars, it is a lot of work. The fx-9860G has plenty of memory - I programmed all that ephemeris on an earlier Casio version with only 36K memory - but you will have to enter literally hundreds of periodic terms by hand, and that is after you figure out how to write the programs. If you want to program these ephemerides yourself, you are going to have to buy Astronomical Algorithms by Meeus and study it pretty intensively. Unless this is something you want to do as an intellectual challenge - like building ships in a bottle or solving all the Sunday Times crossword puzzles- I suggest you buy a program.
The best commercially available navigation calculator I believe is the StarPilot by Star Path. The Lunar Distance algorithm is flawed, but the rest of the program is excellent and is packed with navigation features. You can buy StarPilot loaded on a TI calculator for $299 at Celestair, but nowadays you can just go to the App Store and download it onto your iPhone for only $49.
Wendel Brunner
