NavList:

Thanks Fred for your detailed reply, especially diagnosis of the javascript bug. I think now that I have worked out how to use Pyephem I might abandon Henning's javascript, partly as I feel more confident in using python. My boat computer runs Navigatrix, a special boat version of Linux, so it should be easy to get the python library working and write scripts I like myself. I think there is a CN plug in for OpenCPN and I have yet to try it.

On the other hand one thing I liked about the idea of javascript is the hope that it would run on any phone with a browser, so would be the modern version of using a programmable calculator. I suppose the logical next step is to see if pyephem runs ok with one of the Android versions of python.

Also I will now concentrate on getting the best out of my old Davis Mk 25 plastic sextant. It seems you get lots of practice at adjusting these as I seem to have to adjust all three mirror screws every time I use it.

[By the way sorry I double posted folks. The first one (before I tried python) gave me an error message so I thought it had not gone.]

Best wishes

Bill