JMI Telescopes MOTOFOCUS is a motorized electronic focusing mechanism that affixes to your telescope knob. It installs easily, and can be quickly detached for transport. This particular version works with Celestron's Comet Catcher and SP6 as well as Vixen's R130S and R150S reflectors.
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.