This JMI Telescopes MOTOFOCUS is a motorized electronic focusing mechanism that affixes to the Celestron CPC 1100 telescope. The CPC 1100 has an orange ring at the base of the focuser knob and a 21.8mm diameter knob. It installs easily, and can be quickly detached for transport.
MOTOFOCUS operates off of a supplied 9-volt battery; with a bit of practice, you'll be able to adjust your focuser in increments much smaller than the width of a business card. In particular, springing for the MOTOFOCUS gives you much more enjoyable high-magnification viewing from your scope, with finer control over the image and much less user-induced vibrations.
If you opt for it exclusively at the time of this purchase, you can also have a numerical expression of your focuser position. The economical DFC Digital Focus Counter is an accurate 3-digit mechanical counter which "piggybacks" upon the MOTOFOCUS, and requires no batteries or hand controllers beyond what you'll already be using.
The much more sophisticated DRO Digital Readout is a 4-digit LED that can attach to MOTOFOCUS and other JMI Telescopes focusers. Beyond a finer expression of focus position, the DRO also offers the capacity to be controlled remotely via a computer as well as to be removed and reattached without needing recalibration.
If choosing the DFC or DRO upgrades, you must do so at the time of this purchase-they cannot be retroactively fitted to the MOTOFOCUS.