Engineered for uncompromising precision, the Explore Scientific 3" Self-Centering Focuser is built for demanding astrophotography and visual applications requiring maximum mechanical stability. Whether you’re running a heavy imaging train or pushing your optics to the limit, this heavy-duty focuser offers rock-solid support, buttery-smooth control, and pinpoint accuracy with zero image shift or flex — even under loads of up to 17 lbs.
Machined from black anodized aluminum and weighing 5.7 lbs, the ES-FOC3 features a self-centering compression system that applies even pressure around the drawtube, ensuring perfect alignment and secure accessory placement. The helical rack-and-pinion system, lubricated with marine-grade PTFE silicone, offers fluid movement with minimal backlash — critical for long-exposure astrophotography.
A dual-speed 9:1 reduction knob with stainless steel bearings and clutch protection gives you micro-level focus control, while the internally baffled 3-inch drawtube provides 84.5 mm of travel and compatibility with both 2″ and 3″ twist-lock accessories. The focuser also includes a tool-free rotatable adapter, allowing easy installation and precise angular adjustment on most Explore Scientific refractors (120 mm–140 mm models).
CA Residents: Prop 65 WARNING(S)
⭐ Features & Benefits
- Self-Centering Compression System – Ensures precise, secure alignment of accessories with no tilt or sag
- 3″ Helical Rack-and-Pinion Design – Delivers ultra-smooth focus control with minimal backlash
- Marine-Grade PTFE Lubrication – Withstands temperature swings and heavy use without sticking or slipping
- Dual-Speed 9:1 Fine Focus Control – Stainless steel bearings and clutch safeguard against gear damage
- 84.5 mm Drawtube Travel – Internally baffled for contrast and reduced stray light
- 17 lb Lifting Capacity – Supports large imaging trains without focus shift
- M82 x 1.25 Threaded Drawtube – Allows use of threaded accessories and adapters
- 2″ and 3″ Twist-Lock Compatibility – Accepts a wide range of cameras and eyepieces
- Tool-Free Back Cell Adapter (included) – Secure installation and easy rotation on compatible scopes
- Premium Black Anodized Finish – Built to endure harsh environments and regular transport
🌟 Who It’s For
- Advanced astrophotographers using heavy imaging trains and filter wheels
- Serious visual observers who need rigid focusing for large eyepieces or binoviewers
- Explore Scientific telescope owners upgrading from stock focusers
- **Users needing precise, backlash-free fine focus for planetary, lunar, and deep-sky imaging
- Observatories and outreach programs requiring long-term durability and repeatable results
🛠 Compatibility Notes
- ✅ Compatible out of the box with most black-tube Explore Scientific refractors (120–140 mm)
- ⚠️ White-tube ES scopes with threaded back cells must be shipped to Explore Scientific for adapter installation
- ⚠️ FPL53-165CF requires a separate back cell adapter (sold separately)
- ✅ TED15208CF mounts directly—no adapter needed
🎒 What’s Included
- Explore Scientific 3" Self-Centering Focuser
- Tool-free back cell adapter with hand-turnable mounting knobs
- Brass compression rings and twist-lock eyepiece clamps
- Internal light baffles
- Threaded drawtube (M82 x 1.25 pitch)
- Installation instructions
Specs
| Item Number | ES-FOC3 |
|---|---|
| Lifting Capacity | 17 lbs (7.7 kg) |
| Draw Tube Travel | 84.5 mm (3.32 in) |
| Draw Tube Clear Interior Diameter | 76.2 mm (3 in) |
| Draw Tube Thread | M82 x 1.25 |
| Draw Tube Baffles | 14 |
| Focus System | Helical rack and pinion |
| Reduction Ratio | 9:1 with stainless steel ball bearings and shaft |
| Attachment Mechanism | Self-centering compression system |
| Weight | 5.7 lbs (with 3" to 2" twist-lock adapter) |
| Compatibility with Electric Focusers | Yes |
| Telescope Compatibility | Explore Scientific refractors 120 mm and larger; custom adapters available for other brands |
Warranty Information:
This product is covered by a Limited One-Year USA Warranty, valid when registered within 60 days of purchase. To activate your warranty, please visit the Explore Scientific website and complete the registration form at: