NavList:

Great work Greg,

I think Chichester also did pre-flight Hps using the Bygrave,(but could have used long hand on land.) However, I think he went off course during the flight and had to do some new pre-computed Hps using the Bygrave while flying. Hence the Chichester test .(Is that correct Gary?) Would the Doniol pass that one? Also, he used conventional marine sextant and had to fly very low to get natural horizons while flying the Gypsy Moth biplane single handed.

Also, I like the idea of plotting the Ha directly on the chart and comparing to the  Hps. What about corrections for dip etc? Presumably you could "reverse correct " the Hps to get "sextant pre-computed altitudes"? that would save any mental arithmetic would it not? Assuming constant known height of airplane? But then with a bubble maybe not necessary?

Fascinating stuff. When you guys have time, I would appreciate your thoughts on the Brown-Nassau prototype using Harri's graphs. I think that would pass the Chichester test, but I'll do some more test drives first to confirm this.

Best wishes

Francis