The Crayford focuser design makes very fine adjustments possible, with tolerances up to 100 times better than conventional rack-and-pinion focusers. Its zero image shift and zero backlash makes it outstanding for visual and photographic work and a must for CCD imaging.

JMI recognized the benefits of this design and was the first company to bring it to the amateur market in a commercial product. Many telescope accessory companies have used the design for add-on focusers since JMI first adopted it and it is now being incorporated into many telescopes as standard equipment, as well.

The illustration shows one of Jack Wall’s original design