Lens Type | Doublet Apochromatic Prime Lens |
Focal Length | 559 mm |
Diameter | 81 mm |
Focal Ratio | f/6.9 |
Image Circle | 45 mm |
Focuser | WIFD R&P Focuser |
Focuser Travel Length | 0-77 mm (Ruler to 90mm) |
Adapter Included | M92 Rotator M92 → M63 Adapter |
Optional Flattener | FLAT6AIII 0.8x |
Camera Format | Full Frame APS-C M4/3 |
Total Weight | 4.56 kg / 10.05 lbs |
OTA Weight | 3.55 kg / 7.82 lbs |
Tube Length | 526 mm - 607 mm |
Diagram Reports
Spot Diagram
Longitudinal Aberration
Size Diagram
Parts
- Front Bahtinov Mask Cover
- Lens Cover with Bahtinov Mask
- Dew Shield, retractable – 81 mm
- Dew Shield Locking Screw
- WIFD Focuser [ Tension Adjustment Guide ]
- Focus ruler scale window
- Two Speed 1:10 Ratio Fine Knob
- Fine Knob Protecting Cover
- M4 Screw Holes for Finder Bracket
- Focuser Knob with Temperature Gauge ( Can be removed to attach EAF ) [ EAF Installation Guide ]
- M92 Camera Angle Rotator (CAA)
- CAA Locking Knob
- M92 → M63 Adapter
- M63 Rear Dust Cap
Hardware Parts
Code Name | Image | Quantity | Usage |
 | 2 | Secure the guider to the handlebar | |
| 1 | Secure the dew shield |
Adaption Guide
graph LR CAA(M92 Rotator) -.-> FA ==> F6A F6A(<img src='https://williamoptics.com/cdn/shop/files/P-FLAT6AIII-2.jpg'>Flat 6AIII<br>0.8x) FA(<img src='https://williamoptics.com/cdn/shop/files/M92-M63.jpg'>M92 → M63 Adapter) F6A ==> T(<img src='https://williamoptics.com/cdn/shop/files/TM-NK-F-M48-1.jpg'>T-Mount) ==> C(Camera) F6A ===> AC(Astro-Camera) CAA ==> 2rotolock(<img src='https://williamoptics.com/cdn/shop/files/RotoLock-2-red.jpg'>2” RotoLock) 2rotolock ===>2Dig(<img src='https://williamoptics.com/cdn/shop/files/DIG2-90-1.jpg'>2” Diagonal) ==>2E(<img src='https://williamoptics.com/cdn/shop/files/E-SWA40-1.jpg'>2” Eyepiece) 2rotolock ==>125rotolock(<img src='https://williamoptics.com/cdn/shop/files/RotoLock-1.25-red.jpg' width='10'> 2 → 1.25' RotoLock) ==>1Dig(<img src='https://williamoptics.com/cdn/shop/files/DIG125-90-1.jpg'>1.25” Diagonal) ==>1E(1.25”Eyepiece) click 2rotolock "https://williamoptics.com/products/35-2-rotolock-visual-back-adapter" click 125rotolock "https://williamoptics.com/products/2-125-rotolock-visual-back-adapter" click 2Dig "https://williamoptics.com/products/dura-bright-2-90-dielectric-diagonal" click 1Dig "https://williamoptics.com/products/dura-bright-125-90-dielectric-diagonal" click F6A "https://williamoptics.com/products/flat6Aiii" click 2E "https://williamoptics.com/products/swan-40mm-2-eyepiece" click 1E "https://williamoptics.com/collections/eye-pieces" click T "https://williamoptics.com/collections/adapters"
Operation Guide
Flattener Back Focus Adjustment
- Find the recommended back focus adjustment distance for your flattener.
ㅤ | Back Focus | Adjust Distance | Image Circle |
Flat 6AIII | 60.2 mm | 5.2 mm | ∅ 44.3 mm |
- No matter how complicated the structure of the front part is, please find the back adapter connected to the camera.
- If your setup requires additional back extender, please remove the original part and install the extender.
- Adjust the back adapter to the required distance.
- Tighten the ring against the back adapter.
- Fine Tuning Take a few test shots. According to the aberration pattern of the surrounding star points of your image, you can determine whether to extend or shorten the Flattener back focus.
▲ Camera Sensor Too Close
▲ Camera Sensor Too Far Away
Focuser Tension Adjustment
William Optics focusers are typically smooth and ready to use without any adjustment. For larger telescopes, tightening the Quick Tension Adjustment Knob can help prevent tube slippage. Other than this, we recommend not touching any screws on the focuser. If adjustment is necessary, please consult a qualified technician.
There’s two side to build WIFD focuser tension:
BOTTOM / Rack & Pinion Gear
- Quick tension adjustment knob
- Smoothness adjustment - Pull in (3mm Hex)
- Smoothness adjustment - Push out (2mm Hex)
- Please Don’t Touch
- Top cover screw Can be removed to attach the electronic devices such as EAF (refer to Installing EAF) or be used as a spare.
Telescope models from June 2025 no longer include the top cover screw.
TOP / Focuser Draw Tube
- Focuser Draw Tube Tension Screws Please Don’t Touch
- Guider/Finder bracket mounting screws (2.5mm Hex)
Notice
- When operating the telescope with a motorized focuser, do not overtighten the focuser tension. Excessive tension may damage the focuser mechanism.
- Make small and slow adjustments. Do not turn anything too much at once.
Installing EAF
- Turn the telescope over and remove the Tension screw.
- Remove the top cover screw near the temperature gauge with 2mm Allen key.
Starting from June 2025, new telescope models no longer include the top cover screw. (Skip Step 2)
- Release (don’t remove) two inner knob screws.
- Remove the temperature gauge knob.
- Find the flat side on the shaft and turn it to face the hole.
- Put the 5-6mm Flexible coupling on the shaft and lock the two inner screws.
- Put the EAF body on and lock the two inner screws.
On Step 6 & 7:
Please make sure one of the screws is lock on the flat side (D-cut profile)
- Align the screw holes.
- Lock the four M4 bracket screws.
Care & Safety Instructions
Solar Safety Warning
Never point your telescope or finder scope at the Sun without a proper solar filter securely mounted to the front of the telescope.
Even a brief, unfiltered glimpse of the Sun can permanently damage your eyes or your camera’s image sensor.
Use only front-mounted solar filters made by trusted manufacturers. These filters must cover the front of the telescope’s dew shield securely.
Do not use solar eyepiece filters. They are unsafe and can fail under sunlight.
With the correct solar filter in place, you can safely observe and photograph the Sun without damaging your eyes, your camera, or your telescope.
Telescope Care & Storage
To preserve the optical quality and lifespan of your William Optics telescope, please follow these essential care and storage practices:
- Allow time to acclimate After use, let the telescope adjust to room temperature before storage. During this period, keep the optical tube open and uncovered to allow moisture to evaporate naturally.
- Ensure dryness Make sure the entire telescope is completely dry, especially the optics and interior tube, and free of dew or moisture before putting it away.
- Use proper storage conditions Store your telescope in a dry, dust-free environment with a stable temperature. Avoid high heat or humidity. Dehumidifiers or silica gel are recommended for long-term protection.
- Prevent dust accumulation Always place dust caps on both ends when not in use, or cover the telescope with a clean plastic sheet if it’s not stored in a case.
Following these steps will help maintain optimal performance and prevent damage to sensitive components such as lenses, mirrors, and coatings.
For a detailed cleaning and maintenance guide, please refer to the full article: Cleaning and Maintenance of Telescopes
Clearance Around WIFD Focuser
To avoid interference between the focuser knobs and the mount, make sure the telescope is properly aligned on the mounting rings.
Loosen the rings slightly and adjust the telescope position so that both focuser knobs are level and parallel to the mount. This ensures sufficient clearance from the saddle plate and prevents accidental contact or obstruction during use.
