|The focuser fitted with a 25mm Celestron X-Cel LX eyepiece|
The Crayford telescope focuser design – developed in 1971 by John Wall and named after the Crayford Manor House astronomical society – has a number of important advantages over rack-and-pinion and can be home built out of wood by almost anybody with a bit of patience and the right tools at hand.
Although some prefer to build the design in metal, with the associated advantages, that approach requires specialized metal working tools, generally out of scope for most home builders.
The 2” woodshop design presented here is scalable, has proven to be sturdy, reliable and, most importantly, when built to tight enough tolerances, allows for very precise focusing, even under heavy loads.
I designed this focuser specifically to carry the weight of a Nikon D7100 camera (± 800 gr) on prime focus, which is considerably heavier than even the largest eyepieces. So far, it is holding up admirably.
Even though building this design is probably possible utilizing hand tools only, for tight tolerances the following specialty tools are recommended:
Electrical table saw and/or
Miter saw: electrical table top (enhanced precision wood cutting) and/or manual (PVC cutting)
Belt sander (80 grit belt)
Vertical drill stand
Drill press vice
Hole saw, 54mm (2 1/8”)
Wood drill bits: 1mm, 3mm, 4/4.5mm, 5/5.5mm and 8mm
Thread tapping set