telescope

Crayford focuser

I wasn't satisfied about the standard focuser on my MEADE telescope.

On the Internet I've found several interesting pages about Crayford focusers. The big advantage is that they work very smooth.

In basic bearings are used, 4 of them, together with a "moving" support point there are 5 points of "holding" the focuser tube in place.

After making several drawings and gethering the needed components and material, I started building one.

In fact this isn't a big problem.

I hope the picture will explain how I've build mine.

This first picture showes the mounted focuser. It has to be painted ( black)

This picture gives you a view to the inside. Notice the place of the bearings.

Angle between them is 120 degrees.

These are the some parts of the focuser. Notice the small rubber things. They give some flexability to the mounting of the alunium U profile. Inside this U-profile I've mounted to bronce bearings for the moving axe ( seen here with the two big black knobs on each side. the big alu knob ( right side , middle of picture) holds a strong spring, seen just below the knob, to give some force between the moving axe and the focuser tube.

By turning the knob it is possible to adjust the force of the spring to get a smooth moving without slip.

These are the bearing parts. The height of it was calculated before building it. It is very important to get the focuser tube close to the center of the telescope. I got it at less then 0,5 mm. Looks good to me !

The focuser tube is made out of aluminium (as almost all the parts of this focuser).

It needs a flat surface to get a good grip. To manage a smooth moving I've used a strong, but small spring to keep enough grip, even when the flat surface isn't flat enough. It works prettty good.

The spring is fitted inside the aluminium knob, see picture 3 ( also 1 and 2).