This version of our MicroTouch Direct Drive motor is designed to work with the new TEC Large Focuser. Older TEC scopes use the Feathertouch 3545 focuser and would need the Feathertouch version of our Direct Drive motor.
The TEC Large Focuser has replaced the Feathertouch 3545 on new TEC telescopes. The way in which the fine focus mechanism (and hence the Direct Drive motor) are installed differs from the Feathertouch, but the basic operating principle is the same, and suffers from the same limitations with heavy payloads. The Feathertouch 3.5" focuser is the industry standard for a high-quality, large focuser and is included as standard equipment or an optional upgrade on many different telescopes. However, due to the nature of its fine-focus mechanism, which uses bearing balls for the planetary reduction, the focuser can slip when moving heavy payloads such as a large-format CCD camera with filter wheel, off-axis guider, etc.
The Starizona MicroTouch Direct Drive motor is an upgrade to the standard motor normally included with our MicroTouch autofocuser. The standard motor simply runs a gear mounted to the fine-focus shaft of the Feathertouch, hence it is possible for slippage to occur. With the MicroTouch Direct Drive, the motor assembly bypasses the fine-focus mechanism and runs the focuser pinion directly, eliminating the possibility for slippage.
In order to maintain the precision of the TEC focuser, the MicroTouch Direct Drive uses a high-ratio gear reduction system. This produces an impressive 50:1 focus reduction. The resulting precision is 15000 steps of the motor per turn of the focuser pinion, or just 1.425 microns (0.000056") per step.
How It Works
When you remove the manual focus knobs on the standard TEC focuser to install an autofocus motor, you can see the internal reduction mechanism. The fine-focus shaft is pinched by three stainless steel bearing balls held in a brass housing. When the coarse-focus knob is turned, the brass housing and balls are turned directly. This drives the pinion shaft which moves the focuser drawtube. When the fine-focus knob turns the fine-focus shaft, the balls are turned more slowly because of the difference in radius between the shaft and the bearing balls. This gives the 10:1 fine-focus reduction. Unfortunately, with a heavy load, the drawtube resists the upward pull of the payload against gravity. The fine-focus shaft can then slip against the bearing balls and precision focus ability is lost.
The Starizona MicroTouch Direct Drive avoids this problem by using a high-ratio gear reduction assembly. The motor drives the pinion directly, bypassing the fine-focus mechanism. In this way there is no possibility of the drawtube slipping and focus is much more precise and repeatable.
- 50:1 Fine-Focus Reduction
- 1.425-Micron Step Size
- Rugged, High-Quality Construction
- Compatible with TEC Large Focusers
- Easy Installation
- Made in USA