Athenet

Athenet is a precision instrument for the coastal observer. Standing on a seawall, a dune crest, or a clifftop, you can know with certainty which charted marks — lighthouses, beacons, spires, towers — stand clear of the horizon and which ones the curve of the earth has put below it. Set the bench in three steps: declare your eye height above sea level, choose the state of the air and the day's meteorological visibility, and select the marks you mean to watch. Athenet's Reckoner solves geographic range, luminous range, and apparent elevation for every mark in your register, returning a plain verdict — Shows, Dips, Too Faint, or Occulted — for each one. Results update in real time as you move the limb sliders for eye height, refraction coefficient, and met visibility. All computation runs on your device, entirely offline. No accounts, no subscriptions, no live data feeds. The physics — earth curvature corrected for atmospheric refraction, Koschmieder transmissivity for luminous range — is rigorous and traceable. A cross-section diagram shows the geometry of each mark against the curve of the earth. The height ladder tells you exactly how much eye height you need before a dipping mark comes clear. The back-solve reads your photograph of the seaward view and finds the meteorological visibility that best explains which marks you can and cannot see. Athenet also prints an outlook sheet: a plate showing the full horizon panorama with every mark ticked on it, the station parameters, register verdicts, and the back-solved air. Save it to your photo library before the watch begins. Built for the small-boat sailor checking marks before a coastal passage, the harbour master confirming leading lights, and anyone who reasons carefully about what is above the horizon and why.