ZWO EAF Electronic Auto Focuser
Technical sheet for the ZWO EAF electronic auto focuser (standard version, not Pro): description, specifications and strengths for autofocus in astrophotography.
Description
The EAF (Electronic Auto Focuser) from ZWO is a focus motor that clips directly onto the manual focus knob of an existing focuser (rack-and-pinion, Crayford…), without replacing it. Driven via ASCOM or INDI from acquisition software (NINA, SGP, ASIAIR, SharpCap…), it enables automatic, repeatable autofocus — essential for long-exposure astrophotography.
Note that this is the standard version, not to be confused with the EAF Pro: the Pro adds a built-in physical hand controller, a status LED, a port for a temperature probe, and an internal battery for wireless operation. The standard version relies on a single USB-C cable for both power and data, making it simpler, lighter and cheaper.
Technical specifications
| Specification | Value |
|---|---|
| Type | Electronic focuser (motorized autofocus), standard version (not Pro) |
| Motor | Stepper motor, 1:128 reduction ratio, 7.5° step angle |
| Resolution | ≈ 2.8 µm per step (micron-level precision) |
| Load capacity | Up to 5 kg |
| Shaft diameter (couplers included) | 4 / 5 / 6 / 7 mm |
| Interface | USB-C (power and data over a single cable) |
| Power | 5V, 500mA via USB-C |
| Included cable | USB-C, ≈ 1.5 m |
| Dimensions | ≈ 41 × 52 × 70.3 mm |
| Weight | ≈ 215 g |
| Operating temperature range | -5°C to +50°C |
| Compatible software | ASCOM, INDI — NINA, Sequence Generator Pro, ASIAIR, SharpCap, FireCapture, MaxIm DL, TheSkyX, Nebulosity, FocusMax |
| Box contents | Motor unit, mounting bracket, couplers (4 sizes), screws, hex keys, USB-C cable |
Values from manufacturer specifications, to be refined with real-world use.
Official product page: ZWO EAF
Strengths
- Motorizes focusing without replacing the existing focuser: clips onto the manual knob.
- A single USB-C cable for both power and data, no separate power supply needed.
- ASCOM/INDI compatible: autofocus driven from NINA, SGP, ASIAIR, SharpCap…
- Load capacity up to 5 kg, plenty for a camera + filter wheel imaging train.
- Lighter and cheaper than the EAF Pro for anyone who doesn’t need the built-in hand controller or internal battery operation.
Coming up
This sheet will be expanded with feedback on setup (travel calibration, backlash) and driving autofocus via NINA.