Stumbled on this, very interesting capacitive encoder :
http://www.amtencoder.com/LinkClick....w%3d&tabid=215
some more info on the issue is here:
http://www.amtencoder.com/portals/am...3_TechPres.pdf
The accuracy (don't confuse this with resolution) is a bit low (+-15arcmin - this is 0.5°, the size of the Moon on the sky) but with appropriate up-gearing, it may be significantly improved (for example, 4:1 timing belt pulley should deliver +-3.5arcmin - more than enough for GoTo applications.)
Because of low power consumption and relatively small size (low profile), it may be suitable for placing it inside EQ-6 mount.
It is available on ebay, see here:
http://www.ebay.com.au/itm/AMT102-In...item4cf96b8ec6