Lens Type | 7 Elements Astrograph Design |
Focal Length | 998 mm |
Diameter | 181 mm |
Focal Ratio | f/5.5 |
Image Circle | 55 mm |
Focuser | 3.7” R&P Focuser |
Focuser Travel Length | 43 mm |
Adapter Included | Tilt Adjuster Rotator M48 Camera Adapter M54 Camera Adapter M68 Camera Adapter |
Optional Flattener | No Flattener Required |
Camera Format | Medium Format Full Frame APS-C M4/3 |
Total Weight | 18.7 kg / 41.23 lbs |
OTA Weight | 15 kg / 33.07 lbs |
Tube Length | 1231 mm - 1496 mm |
Diagram Reports
Spot Diagram
Longitudinal Aberration
Size Diagram
Parts
- Lens Cover
- Dew Shield, retractable – 265 mm
- Dew Shield Locking Screw
- Cosmos Steering Wheel
- 3.7” R&P Focuser [ Tension Adjustment Guide ]
- 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 ]
- Sensor Tilt Adjuster [ Adjustment Guide ]
- Camera Angle Rotator (CAA)
- CAA Locking Knob
- M48 adapter with adjustable back focus mechanism ( M54, M68 Adapter interchangeable )
- M48 ( M54, M68 ) Rear Dust Cap
Operation Guide
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 R&P focuser tension:
BOTTOM / Rack & Pinion Gear
- Quick tension adjustment knob
- Smoothness adjustment - Pull in (3mm Hex)
- Smoothness adjustment - Push out (2mm Hex)
- Top cover screw Can be removed to attach the electronic devices such as EAF (refer to Installing EAF)
- Please Don’t Touch
TOP / Focuser Draw Tube
- Focuser Draw Tube Tension Screw - 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.
- Only adjust focuser smoothness if necessary. Incorrect adjustments may affect focusing accuracy or cause mechanical issues.
- Make small and slow adjustments. Do not turn anything too much at once.
Sensor Tilt Adjustment
- Locate the pair of diagonally opposing screws corresponding to the affected corners.
Where is the tilt adjuster?
1. Remove the rotator knob.
2. Remove the ring cover.
3. The tilt adapter is inside.
- Use the 2mm hex key to loosen the pull-in screw of the screw group closest to side where stars appear too close, and loosen the push-out screws of the group on the opposite side (too far).
- Adjust the push-out screws in the "too close" group and the pull-in screw in the "too far" group until the tilt is corrected.
- Gently snug all screws to hold the final position.
Note
- Make small adjustments at a time—1/8 turn is recommended for fine control.
- Adjust other screws if necessary to maintain overall balance.
- If the tilt becomes worse or is severely misaligned, perform a reset:
1. Loosen all push-out screws
2. Tighten all pull-in screws fully
3. Back out each pull-in screw by the same number of turns
4. Begin tilt adjustment again from this neutral position
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
