I own a 900GTO mount that I have been using for a decade. I have upgraded to the CP4 controller, RAPAS and done maintenance to keep it running perfectly. I have a 1100GTO mount with absolute encoders on order. It adds about 50% more to the cost of the mount. I will be keeping my 900GTO so I can use it in my light polluted home observatory for EAA and take the 1100 to dark sky star parties where I can leave it setup for 4-8 nights at a time.
Here is my understanding of the advantages.
No periodic error, zero backlash on axis movements.
67+ million unique positions marked on each axis to allow for sub arc second accurate positioning of each axis at all times.
Closed loop system correcting axis position hundreds of times per second. Data can be use to respond to wind gusts other transient forces affecting axis position.
Using APCC Pro and APPM pointing model with atmospheric pressure, humidity and temperature data to account for atmospheric refraction, custom tracking rates can allow longer unguided exposures.
Mount position is always known as long as the clutches are locked down on the 1100 or 1600 mounts. Mach 2 clutches can be released and not affect absolute encoders.
The cost of the 1100 mount is not insignificant and another 50% increase for encoders makes the choice even harder for many. The value of the system is an individual choice and there are factors such as how much value it provides to the owner and the economic impacts of the purchase on the owner.
Edited by JMW, 23 February 2021 - 01:31 PM.