A lightweight and easy to build 1.25" crayford focuser
Taking inspiration from how the 2” focuser built for K2 (see : Heavy modifications to the 200mm f/3.52 dob’s upper cage. ), I have drawn a 1.25” crayford focuser for an upcoming ultralight dob build.
It is very simple in terms of BOM and assembly. Three parts need to be printed :
- The main body (in gray)
- The upper arc (in gray)
- The draw tube (in brown)
The needed vitamins / hardware are :
| Design. | Precisions | Quantity |
|---|---|---|
| M3 screw | Length 20mm | 4 |
| 623zz bearing | 4 | |
| Knitting needle | dia 3.5mm, smooth | 1 |
| M4 screw | length > 20mm | 1 |
| Copper strip | used for eyepiece compression | 1 |
| M5 screw | nylon tipped, knobbed | 1 |
| Aluminum strip | 58x10x2mm | 3 |
The files are downloadable here :
It handled precisely moving my Hyperion zoom eyepiece (300g), even upside-down (which doesn’t occur in practice), while only weighing 100g with my printer settings (3 perimeters, 0.2mm layer height, 30% gyroid infill).
Here’s a bad picture of the yellow PETG prototype, awaiting to be re-printed and mounted on a scope :
Feel free to reuse the files as I declare them licensed under CC-0. Happy new year.