The joys of having to do all the navigation calculations using logs has never been forgotten.
Great Circle Distance Formula using decimal degrees:
3963.0 * arccos[sin(lat1/57.2958) * sin(lat2/57.2958) + cos(lat1/57.2958) * cos(lat2/57.2958) * cos(lon2/57.2958 -lon1/57.2958)]
And taking sights six times a day was fun. No calculators then.
HAC.MZD=HAV TZD-HAV COS L COS D
Where
MZD = Meridian Zenith Distance TZD = True Zenith Distance H = Local Hour Angle L = DR Latitude D = Declination