










Ultra-Cat 108
The William Optics UltraCat108 is a cutting-edge 108mm apochromatic refractor designed for astrophotographers who demand top-tier performance. Featuring a 5-element advanced Petzval optical design and a fast f/4.8 focal ratio, it delivers breathtaking edge-to-edge clarity and vivid detail, making it perfect for capturing expansive celestial views. Its robust build, exceptional optics, and innovative features redefine the standard for astrophotography.
Key Features:
Advanced 5-Element Petzval Design
Eliminates field curvature, providing sharp, flat-field images without requiring additional flatteners.
60mm Superior Image Circle
Fully supports full-frame and medium-format cameras for wide-field and detailed astrophotography, outperforming standard 106mm telescopes.
F/4.8 Fast Optics
Offers exceptional light-gathering capability for vibrant deep-sky photography.
WIFD (William’s Internal Focuser Design)
Patented internal focuser ensures precise, stable, and hassle-free imaging, avoiding balance issues and eliminating vignetting.
Anti-Shrink Lens Cell Technology
Minimizes thermal expansion and contraction, maintaining perfect optical alignment in any environment.
Sensor Tilt Corrector
Integrated and patented design eliminates distortion, optimizing sharpness and detail for professional-level results.
Built-In Patented Bahtinov Mask
Simplifies focusing for pinpoint precision, a feature that sets it apart from competitors.
Patented Handle Bar Design
Combines ergonomic usability with enhanced portability.
Personalized Laser Engraving
Free customization for direct purchases, adding a personal touch to your telescope.
Accessory Add-ons
Guider










UniGuide 32mm f/3.75
- Lens Type
- Doublet Lens
- Focal Length
- 120 mm
- Diameter
- 32 mm
- Focal Ratio
- f/3.75
- Tube Length
- 147 mm
- Total Weight
- 0.23 kg / 0.51 lbs





Guiding Scope 50mm f/4.0
- Lens Type
- Doublet Lens
- Focal Length
- 200 mm
- Diameter
- 50 mm
- Focal Ratio
- f/4.0
- Tube Length
- 252 mm
- Total Weight
- 0.42 kg / 0.93 lbs










UniGuide 50mm f/4.0
- Lens Type
- Doublet Lens
- Focal Length
- 200 mm
- Diameter
- 50 mm
- Focal Ratio
- f/4.0
- Tube Length
- 252 mm
- Total Weight
- 0.5 kg / 1.1 lbs








GuideStar 61
- Lens Type
- Doublet APO Prime Lens
- Focal Length
- 360 mm
- Diameter
- 61 mm
- Focal Ratio
- f/5.9
- Image Circle
- 42 mm
- Focuser
- Threaded Focuser
- Adapter Included
- M54 → 2" Visual Back
- Optional Flattener
- FLAT 61A 1.0x FLAT 61R 0.8x
- Tube Length
- 340 mm
- Total Weight
- 1.44 kg / 3.17 lbs
Camera




ZWO ASI 533MC Pro
- Sensor
- Sony IMX533 CMOS ( color )
- Resolution
- 3008 × 3008
- Pixel Size
- 2.9μm
- Sensor Size
- 1″ ( 11.31 x 11.31mm )
- Max Frame Rate
- 20 fps
- Read Noise
- 1.0e
- Cooling Temp
- △35°C
- Quantum Efficiency
- 80%
- Full Well
- 50ke
- Exposure Range
- 32μs–2000s
- DDR3 Buffer
- 256 MB
- ADC
- 14 bit
- Flange Distance
- 17.5mm
- Camera Thread
- M42
- Adapter Included
- M48 → M42 Adapters ( 0 & 16.5mm ) M42 Extender ( 21mm ) M28.5 → M42 Adapter 1.25" Nosepiece → M42 Adapter
- Interface
- USB 2.0 Type-A USB 3.0 Type-B
- Cable Included
- USB 2.0 Type A↔B ( 0.5m ) x2 USB 3.0 Type A↔B ( 2m )
- Camera Weight
- 0.457 kg / 1 lbs
Camera Adapter



M48 T-mount for Pentax K
- Light-In Side
- M48 (female)
- Light-Out Side
- Pentax K Camera Mount
- Optical Length
- 9.3 mm



M48 T-mount for Canon EOS R Mirrorless
- Light-In Side
- M48 (female)
- Light-Out Side
- Canon EOS R Camera Mount
- Optical Length
- 34.4 mm



M48 T-mount for Nikon Z Mirrorless
- Light-In Side
- M48 (female)
- Light-Out Side
- Nikon Z Mirrorless Camera Mount
- Optical Length
- 38.4 mm






M48 T-mount for Canon EOS
- Light-In Side
- M48 (female)
- Light-Out Side
- Canon EOS Camera Mount
- Optical Length
- 10.6 mm



M48 T-mount for Fuji FX
- Light-In Side
- M48 (female)
- Light-Out Side
- Fuji FX Camera Mount
- Optical Length
- 37 mm



T-mount for Sony E
- Light-In Side
- M48 (female)
- Light-Out Side
- Sony E Camera Mount
- Optical Length
- 36.7 mm






M48 T-mount for Nikon F
- Light-In Side
- M48 (female)
- Light-Out Side
- Nikon F Camera Mount
- Optical Length
- 8.2 mm



M48 T-mount for Olympus Micro 4/3
- Light-In Side
- M48 (female)
- Light-Out Side
- Olympus Micro 4/3 Camera Mount
- Optical Length
- 35.6 mm


M48 → M42 Adapter
- Light-In Side
- M48 (female)
- Light-Out Side
- M42 (male)
- Optical Length
- 5.3 mm
EQ Mount









ZWO AM3 RedCat Limited Edition
ZWO x William Optics Co-branded Limited Edition
Traditional equatorial mounts often require heavy counterweights, making it challenging to balance the right ascension (RA) and declination (DEC) axes. They are cumbersome to transport and store, causing significant inconvenience for amateur astrophotographers during outdoor sessions. Additionally, some strain wave gear mounts have limited functionality, insufficient payload capacity, and lack stability during use. Addressing these issues, ZWO has developed the ASI Mount series, which eliminates the need for counterweights.
The AM3 weighs only 3.9 kg and supports payloads ranging from 8 kg to 13 kg. While portability is crucial, ZWO prioritizes stability to ensure a reliable user experience. The optimized internal structure incorporates harmonic drive reducers and timing belts, delivering precise control and an impressive 300:1 reduction ratio. The mount is versatile, functioning as either an equatorial or an alt-azimuth mount, and can be controlled via Wi-Fi, Bluetooth, or a handheld controller.
Key Features
Portability and Stability
The optimized internal structure, featuring harmonic drive reducers and timing belts, ensures precise control and stability, achieving a remarkable 300:1 reduction ratio.
Custom Strain Wave Gears
ZWO developed specialized strain wave gears tailored to astrophotography needs, offering extremely low periodic error and high torque. Each mount undergoes factory testing and comes with a unique PE curve to guarantee quality.
Lightweight Design
At just 3.9 kg, the AM3 strikes a balance between portability and stability, prioritizing dependable performance over extreme weight reduction.
8 kg to 13 kg Payload Capacity
Without Counterweights: Supports up to 8 kg.
With Counterweights: Supports up to 13 kg.
(Counterweights should be mounted on a bar no longer than 20 cm.)
Dual Modes: Equatorial and Alt-Azimuth
Equatorial Mode: Ideal for tracking and imaging celestial objects.
Alt-Azimuth Mode: Best suited for visual astronomy.
Easily switch modes using the ASI Mount App or the handheld controller.
Full 0°–90° Altitude Adjustment
Gear 1: Adjust the handle to set angles between 0° and 60°.
Gear 2: Loosen the hex screws to adjust the clamp for angles between 30° and 90°.
Wireless Control
Enjoy features like Tonight’s Target, GOTO, and Live Preview directly from your smartphone via Wi-Fi.
Joystick Hand Controller
Ergonomically designed for comfort and ease of use, the controller integrates with the Wi-Fi network for wireless operation. Firmware updates and installation can be managed effortlessly via a web interface.
Seamless ASIAIR Integration
The AM3 can be controlled via wired or wireless connection with ASIAIR, offering ZWO’s customers an optimized astrophotography experience.







ZWO AM5N RedCat Limited Edition
ZWO x William Optics Co-branded Limited Edition
Traditional equatorial mounts often require heavy counterweights, making them cumbersome to transport and balance. The AM5N addresses these challenges with a compact, counterweight-free design, offering enhanced portability and stability for amateur astrophotographers. Its optimized internal structure incorporates harmonic drive reducers and timing belts, delivering precise control and a 300:1 reduction ratio. The mount operates in both equatorial and alt-azimuth modes and can be controlled via Wi-Fi, Bluetooth, or a handheld controller.
Key Features
Enhanced Portability and Stability
Weighing only 5.5 kg, the AM5N supports payloads up to 15 kg without counterweights and up to 20 kg with counterweights, maintaining a balance between portability and performance.
Custom Harmonic Drive System
The AM5N features a custom harmonic drive system with a synchronous belt, ensuring high torque, zero backlash, and low periodic error of ±10 arcseconds.
Integrated Cable Management
Internal cable routing through the DEC saddle allows for seamless power and control connections, reducing cable clutter and the risk of snags during operation.
Dual Mount Modes
Switch effortlessly between equatorial and alt-azimuth modes using the ASI Mount App or the included hand controller. A status LED indicates the current mode: red for equatorial and green for alt-azimuth.
Wide Latitude Adjustment
The mount offers a full 0°–90° latitude adjustment range, accommodating various observing locations and setups.
Wireless and Wired Control Options
Control the AM5N via Wi-Fi, Bluetooth, or USB-C connections. The mount is compatible with the ASIAIR system and supports ASCOM and INDI protocols for versatile operation.
Power Failure Protection
An RA axis brake system engages automatically during power failures, safeguarding your equipment from potential damage.
Seamless ASIAIR Integration
The AM5N integrates seamlessly with ZWO's ASIAIR system, providing an optimized astrophotography experience through wired or wireless connections.




Tripod







Pier Mount 90
- Adapter
- 3/8" Thread ( for ZWO AM3/AM5 )
More EQ Mount types are optional - Weight
- approx. 7 kg
- Loading Capacity
- 90 kg / 198 lbs
- Height
- Stance: 89.3 cm Closed: 79.3 cm Foot Adjustable Height Range: 15 mm
- Material
- Aluminum Alloy
- Pillar Diameter
- 100 mm / 4"
![[Bundle] ZWO Mount Upgrade Kit](http://williamoptics.com/cdn/shop/files/ZWOMountUpgradeKit.jpg?v=1724140371&width=2400)
[Bundle] ZWO Mount Upgrade Kit
Make your ZWO AM3/5 tripod kit load-bearing and stable.


Tripod Extrapadding Backpack
This Tripod Extrapadding Backpack is specifically designed for astro EQ mounts tripod, offering added support and protection for your equipment.
- Thickness: 22mm
- Size: approximately 20 × 20 × 67 cm, with a measurement tolerance of ±3 cm.














Camouflage Tripod Pouch
Featuring durable Velcro straps for secure attachment, this pouch offers ample storage space to make your wildlife observation experience more convenient.
- Lens Type
- 5-Element Advanced Petzval
- Lens Elements
- Super ED Glass x2 ED Glass x1 Lanthanum Glass x1 X-Element x1
- Focal Length
- 518 mm
- Diameter
- 108 mm
- Focal Ratio
- f/4.8
- Image Circle
- 60 mm
- Focuser
- WIFD R&P Focuser Compatible with EAF
- Focuser Travel
- 0-30 mm (Ruler to 31mm)
- Adapter Included
- Sensor Tilt Xterminator Rotator M68, M54, M48 Camera Adapters
- Optional Flattener
- No Flattener Required
- T-Mount Support
- Canon EF, RF Nikon F, Z Sony E Pentax K MFT (M4/3) FUJI X
- Camera Format
- Medium Format Full Frame APS-C M4/3
- Dovetail Type
- Losmandy
- Tube Length
- 512.9 mm - 617.9 mm
- OTA Weight
- 7.96 kg / 17.55 lbs
- Total Weight
- 9.58 kg / 21.12 lbs
Choose options











The William Optics UltraCat108 is a cutting-edge 108mm apochromatic refractor designed for astrophotographers who demand top-tier performance. Featuring a 5-element advanced Petzval optical design and a fast f/4.8 focal ratio, it delivers breathtaking edge-to-edge clarity and vivid detail, making it perfect for capturing expansive celestial views. Its robust build, exceptional optics, and innovative features redefine the standard for astrophotography.
Key Features:
Advanced 5-Element Petzval Design
Eliminates field curvature, providing sharp, flat-field images without requiring additional flatteners.
60mm Superior Image Circle
Fully supports full-frame and medium-format cameras for wide-field and detailed astrophotography, outperforming standard 106mm telescopes.
F/4.8 Fast Optics
Offers exceptional light-gathering capability for vibrant deep-sky photography.
WIFD (William’s Internal Focuser Design)
Patented internal focuser ensures precise, stable, and hassle-free imaging, avoiding balance issues and eliminating vignetting.
Anti-Shrink Lens Cell Technology
Minimizes thermal expansion and contraction, maintaining perfect optical alignment in any environment.
Sensor Tilt Corrector
Integrated and patented design eliminates distortion, optimizing sharpness and detail for professional-level results.
Built-In Patented Bahtinov Mask
Simplifies focusing for pinpoint precision, a feature that sets it apart from competitors.
Patented Handle Bar Design
Combines ergonomic usability with enhanced portability.
Personalized Laser Engraving
Free customization for direct purchases, adding a personal touch to your telescope.
What's in the box

Main Tube

Bahtinov Cap

M48, M54, M68
Camera Adapter

Vixen-style Plate

Mounting Ring & Handle bar

Soft Carry Case

Allen Key Set

Let the quality speaks
The UltraCat 108 embodies the pinnacle of optical engineering, merging a revolutionary 5-element Petzval design with cutting-edge features tailored for astrophotographers. Every detail—from its expansive image circle to its internal focuser and integrated tilt corrector—is crafted to deliver unmatched clarity, precision, and performance across the celestial canvas.

Advanced Petzval
Extra-low Dispersion (ED) glasses


Needs NO Flattener
Never easier to capture deep sky objects



Compatible with Electronic Motorized Devices
Hassle Free Installation
( No Mounting Bracket Kit required )
The new K-ASTEC mounting bracket (optional) is now avalible to make the EAF more streamline with the OTA.
Leading the market
Wo patented design
The Ultra-Cat 108 holds three unique patents, ensuring easy and perfect focusing along with precise coaxial image quality, preventing draw tube tilt issues caused by optical misalignment.
:
Internal Focuser


Integrated Bahtinov mask
CAT Handle Bar
Crafts for enhanced portability and versatility.
Mounting Ring
Designed for seamless functionality without compromising on stability. Engineered with wide surface contacts, this innovative ring ensures a secure fit while enabling fast, easy detachment.



















