| This electric focuser for the ETX-90 and ETX-105 is particularly useful when viewing near the zenith (in the standard altazimuth mode) because it is difficult to reach the focus knob between the fork arms when your scope is in this position. This is particularly true when wearing gloves or mittens in the fall or winter. Because of the close quarters at the back of the scope, focusing is done by means of a belt drive from a miniature motor rather than a motor directly mounted on the scope’s focus knob. The very compact focus motor and gear box (it measures only 1" x 0.5" x 0.375") is mounted along the body of the scope rather than projecting from the focus knob, as shown in the feature image below. This mounting position keeps it out of your way when observing. The rubber O-ring drive belt turns a new large focus knob for a finer focusing capability than is possible with the scope’s standard small knob. The electric focus motor gives precise, vibration-free focusing without the need to touch the telescope. The rubber belt drive is easily removed in a matter of seconds, allowing manual focusing at any time. Mounting is easy with no drilling or tapping, using one of the existing holes in the rear cell of the scope. The focuser comes with a Pulse-Width Modulation (PWM) hand control that contains a 9-volt transistor radio battery (supplied) with a life expectancy of 6-8 months in normal use. Pushbuttons control the direction of focuser travel. The hand control has a small three-position (high / medium / low speed) slide switch that adjusts the motor’s speed for very precise fine adjustment of the focus when the directional buttons are pushed. The three slow speeds each ramp up to high speed if the directional button is held down for two seconds. This lets you make major focus changes quickly, without giving up the precision fine correction ability. Quick-stop electromagnetic braking avoids overshooting the focus point at all speeds. The focuser comes with all necessary tools and hardware to install the focuser (a matter of about 10 minutes). You get the focus motor, a new larger focus knob, the hand control (with battery), connecting cable, and the drive belt (with a spare).
MOTOFOCUS is especially important for the ETX when viewing near Zenith (in Alt/Az mode) because it is very hard to reach the focus knob at this position. We use miniature motors (motor and gear box size is 1" x 0.5" x 0.375"!) for a very small package.
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