[rogerg (Roger)]

Originally Posted by mithrandir

It's another two motors, would rely on the tripod/pier head being perfectly level, known local magnetic variation, and a CCD to confirm the alignment stars were where it though they should be.

I don't see that it should rely on tripod/pier level at all - the fact is you could have a level in the tripod knowing how "off level" it is, this could be taken into consideration quite easily I think.

Originally Posted by mithrandir

Any magnetic compass is only as accurate as the variation you feed it. A bit of reo in the concrete or a nearby steel fence throws my Silva compass off about 5 degrees. Polar alignment needs better values than "S is over thataway".

Interesting. I don't have an iPHone to test it, but I thought if magnetic interference would be a problem then the electronics, battery, metal in a device like an iPhone would have the same effect as reo, if it did affect the type of compass used in such devices?

Originally Posted by mithrandir

With a bit of practice it doesn't take that long to polar align, at least for visual.

Of course that's true, but the same could be said for Goto: It doesn't take much to learn star hopping to the point it's extremely efficient to find almost any NGC object, but people still like Goto

Thanks for your reply, all interesting food for thought