The focuser consists of a DC motor with mounting bracket and a focusing collar with internal O-ring coupling to electrically turn your manual focuser knob, a hand control, and all necessary mounting hardware.

One of the telescope focuser knobs is removed using the supplied Allen wrench and the focusing collar of the JMI focuser is pushed onto the manual focuser’s exposed drive shaft until the rubber O-ring inside the focusing collar grips the focuser shaft firmly. The rubber O-ring provides a secure grip on the telescope’s focus knob to turn the focuser under the command of the electric focuser’s hand control pushbuttons. The O-ring also acts as a slip clutch to allow manual operation of the focuser using the focuser’s second knob, as well as preventing damage if the normal telescope focuser travel is exceeded.

Two screws in the rack and pinion cover of the scope’s focuser are removed and the mounting holes in the JMI focuser bracket are lined up with the exposed screw holes. The screws you removed from the scope’s focuser are reinstalled through the electric focuser’s mounting bracket to hold the JMI focuser in place.

A coiled cord permanently attached to the push-on motor plugs into the hand control unit. The control box holds a 9-volt battery (supplied) that will power the focuser for 6 to 8 months of normal use. Pushbuttons control the direction of focuser travel, while a three-position slide switch variable speed control adjusts the focusing speed. The slow and medium focusing speeds automatically switch to high speed focusing if the focus button is held down for more than three seconds. The motor has electromagnetic braking for very precise control.