The true position of the mount is determined by the motors microstep count relative to home, but this "home" can be changed as required
The encoders in the EQ8 ( And EQ6/5) are very coarse ( around 80 arcsec/ pulse for the EQ8 and 250 arcsec per pulse for the others )
They are only really used when "freedom finding", ie if you declutch the axes and manually slew around, they will keep your alignment "roughly" accurate ( by changing the microstep datum point ), but it may be several arcmins off. This is OK if rubbernecking, but not if you are synchronised with a planetarium program and require accurate positioning data.
The encoders have nothing to do with tracking rates etc, but as noted above, they can automatically change the microstep baselines if they trip certain limits, ie even tho the mount hasnt moved from target, the encoder can tell the system it has moved and adjust its datums without asking :-)
As such, unless you are rubbernecking, they really are not required.
Andrew Johansen Melbourne Australia
Edited by OzAndrewJ, 18 September 2019 - 12:42 AM.