ZWO EAF Bracket for GSO Newtonian focuser with curved mounting surface

thingiverse

This is a bracket that allows you to mount a standard ZWO EAF (Electronic Auto Focuser) onto a GSO-made Newtonian focuser. GSO makes Newtonians for many brands including Orion and others. I would say most Newtonian Astrographs are GSO-made and then re-branded. For years, GSO made focusers that had a concave surface where you would mount the EAF bracket, making mounting a challenge. Only within the last year or two did they change the design to feature a flat mounting surface. But there are probably 10-20 years worth of Newtonians out there with the previous design and this bracket is intended for those. The bushing is used to keep the shaft centered where it exits the GSO focuser housing on the left side (normally the focus knob would do that but you are removing the knob to install the EAF). The Shaft Coupler is sized perfectly to accept the EAF shaft on one side and the ZWO shaft on the other. You can use an aluminum shaft coupler from ZWO that come with the EAF instead, and their benefit is that they have slots cut into them that allow for some bending in case of imperfect shaft alignment, however, the hole size of the ZWO coupler is not ideal for the GSO focuser shaft - it's a bit too big. It will still work but this is why I designed a 3D printed coupler that is perfectly sized. It has no flex though, so try to get the shaft alignment as good as you can. You will need to buy some M4 grub screws and drill and tap the holes in the couple for the grub screws - the holes are there but need to be sized up just a tiny bit. If you buy a drill & tap kit for M4, that is what you will use. I suggest using a very hard plastic in order to support the pressure from the grub screws. I used a carbon-fiber fortified filament and it has worked well.You will need longer allen-head cap screws to mount the focuser bracket.