The ZWO 1.25" Helical Focuser brings controlled, manual fine focusing to a compatible off-axis guiding setup. Designed for the ZWO OAG and ASI Mini cameras, it lets you adjust guide-camera focus without rotating the camera holder—helpful when you want to preserve camera orientation and keep cables neatly routed.
Its 6 mm focusing travel provides a useful final adjustment once the guide camera is close to focus. A graduated focusing collar makes it easier to judge small changes while watching your guide-camera preview.
Fine focus without turning the camera
- Non-rotating adjustment: the camera holder maintains its orientation as you focus.
- 6 mm manual travel: refine guide-star focus after setting the approximate camera position.
- 1.25" pass-through design: intended for compatible 1.25" guide-camera barrels, including the ASI Mini range.
- M42 × 0.75 female connection: a threaded mounting interface for a matching male T2 connection.
- Graduated collar: a visual reference when making and repeating small adjustments.
Check your guiding setup before ordering
ZWO specifies this focuser for its OAG and ASI Mini cameras. Compatibility with another off-axis guider depends on its mounting thread, clearance and available guide-camera spacing. A 1.25" camera barrel alone does not establish compatibility.
The mounting connection is M42 × 0.75 female, and ZWO gives a minimum overall height of 48.5 mm. Check the complete mechanical arrangement before purchase, especially where space around the guide port is limited. Overall height should not be treated as a universal optical back-focus requirement.
The 6 mm range is for fine adjustment. It cannot compensate for every mismatch between the main imaging camera and guide-camera focus positions. Any required adapters, spacers, off-axis guider and camera must be selected for your particular system.
A practical focusing sequence
- Focus the main imaging camera first.
- With the guide camera securely fitted, establish an approximate guide-camera position close enough to reach focus.
- View a star in the guide-camera preview and turn the helical focusing collar in small steps.
- Secure the camera and recheck the star image before starting a guiding session.
This is a manual mechanical focuser. It does not provide motorised or software-controlled autofocus.
Specifications
| Manufacturer | ZWO |
|---|---|
| Product | 1.25" Helical Focuser |
| Focusing method | Manual helical adjustment |
| Camera-holder movement | Non-rotating during focus adjustment |
| Camera barrel format | 1.25" |
| Mounting thread | M42 × 0.75 female (T2) |
| Focusing travel | 6 mm |
| Minimum overall height | 48.5 mm, as specified by ZWO |
| Manufacturer's intended pairing | ZWO OAG and ASI Mini cameras |
Choosing the right accessory
Browse our ZWO accessories for related equipment. If you are unsure about fit, contact Dark Clear Skies with your off-axis guider model, guide camera and connection details before ordering.
Frequently asked questions
Will the camera rotate when I adjust focus?
No. The non-rotating holder is designed to maintain camera orientation while the helical mechanism changes the focus position.
Will it fit every off-axis guider?
No universal fit is claimed. ZWO identifies its OAG and ASI Mini cameras as the intended combination. For another guider, check the matching M42 × 0.75 thread, physical clearance and guide-camera spacing.
Does it focus my main imaging camera?
In the intended off-axis guiding arrangement, it adjusts the guide-camera focus. Focus the main imaging camera separately, then bring the guide camera into focus.
Are the guide camera and OAG included?
No. This listing is for the helical focuser; the camera and off-axis guider are separate equipment.