eFinder code gets revisited

With more people using the eFinder in the field, some bugs have emerged. The list presents some lessons to the amateur code writer (me!).

Stupid maths errors (or poor checking)
Not enough attention to detail in interface protocols 
Relying on imported methods without checking their performance.
Implementing too many changes at the same time.

Biggest issue has been with my use of PyEphem to do the many coordinate transformations between RADec & AltAz. Originally I was doing these the hard way with my own code. Then I discovered PyEphem and it got a whole lot easier and neater. Only trouble is the results arent consistent. Spent weeks trying to get them right as there are many variable that can be set, but gave up. PyEphem was deprecated in 2003 and I guess its no longer using the right dependencies.  Fortunately the author had meanwhile produced Skyfield . This at first seemed very complicated but as usual with these things with a bit of patience I got my head around its principles and ended up getting sub-arcsecond consistency.

So I’m now in the middle of re-writing all the eFinder variants to use Skyfield, and incorporate the many bug fixes.

© AstroKeith 2022