JMI Reverse Crayford Focuser

JMI SKU: RCF1
rcf_1_b (6795784847513)
rcf_1_f (6795784847513)

JMI Reverse Crayford Focuser

JMI SKU: RCF1
Regular price $149.00 Sale price $119.20 Save $29.80
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JMI Reverse Crayford Focuser is a light-weight, low-profile 2" focuser with a new revolutionary design - JMI's low-cost, high-quality answer to plastic focusers.

JMI Reverse Crayford Focuser


JMI Reverse Crayford Focuser is a light-weight, low-profile 2" focuser with a new revolutionary design - JMI's low-cost, high-quality answer to plastic focusers. In the reverse Crayford design, the drive-shaft pressure is applied to a bar which "pulls" the drawtube against its supporting bearings as apposed to directly "pushing" the drawtube as seen in the normal Crayford design. This design gives zero image shift and zero backlash as with our EV focusers.

The highly acclaimed Crayford design uses high pressure on a metal drive shaft pressing against a 3" metal drawtube which is held by bearings on the opposing side. This direct surface-to-surface drive mechanism eliminates backlash and shifting of the drawtube as seen in other designs such as the rack-and-pinion focuser, and allows for very fine adjustments.

A flat or curved base choice must be specified up on purchase. For curved bases, you need to specify the radius. If you don’t, you will get the standard size radius. The Reverse Crayford Focuser has a standard radius of 10 inches (5" diameter).

Please place a note in the shopping cart comments area specifying “Flat Base” or “Curved Base” and the appropriate radius for the curved base (Diameter = 2 x Radius).

Note: When using a laser collimator, keep in mind that there will be slight deviations in the laser beam when moving the drawtube through the full length of travel. This deviation is not noticeable visually, is only a small fraction of the amount present with a normal rack-and-pinion focuser and is completely eliminated with the higher quality of the EV focusers. Due to the design of this focuser, the knobs are at a 90-degree orientation from most, placing the drive shaft perpendicular to the optical tube when using a curved base.

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