This is a reducer designed specifically for PlaneWave CDK flat field telescopes. This reduces the f ratio of the CDK telescope 66%. The CDK12.5 f/8 telescope will be reduced down to f/5.3. The CDK14 will be f/4.8 and for CDK17 f/6.8 will be reduced to f/4.5
Note: 125166 adapter is compatible with CDK17 that have 10.24″ back focus. CDK17 with 8.81″ back focus will use the 200166 focal reducer.