The William Optics Ultra-Cat 108 is a premium refractor telescope designed with serious astrophotographers in mind. Combining cutting-edge optical technology, a user-friendly design, and high-quality construction, this telescope delivers outstanding performance for capturing stunning images of the night sky. Whether you’re photographing nebulae, galaxies, or star clusters, the Ultra-Cat 108 is built to meet the demands of both amateur and professional astrophotographers.
Advanced Optical Design
At the heart of the Ultra-Cat 108 is a sophisticated five-element Petzval optical system. This system includes two Super Extra-low Dispersion (ED) glass elements, one regular ED glass element, one Lanthanum glass element, and one additional X-Element. Each of these elements is chosen for its unique ability to correct optical distortions.
Together, these components eliminate common imaging problems like chromatic aberration (color fringing), coma (streaked stars near the edge), and field curvature. The result? You get extremely sharp images with accurate colors and edge-to-edge clarity.
This level of optical correction is especially beneficial for astrophotographers using large sensors, as the image quality remains excellent across the entire field of view.
Wide Aperture and Fast Optics
The telescope has an aperture of 108mm (4.25 inches), which gives it the ability to gather a substantial amount of light. A larger aperture allows more photons to hit the camera sensor, improving image brightness, contrast, and detail, especially important when photographing faint deep-sky objects.
Its focal length is 518mm, resulting in a fast focal ratio of f/4.8. Fast optics like this are ideal for astrophotography because they reduce exposure times while still capturing fine details. You can capture more data in a shorter time, making the most of each clear night.
Large 60mm Image Circle
One of the standout features of the Ultra-Cat 108 is its enormous 60mm image circle. This makes it compatible with full-frame and even medium-format sensors, giving photographers a wide, flat field that’s free of vignetting and distortion.
For wide-field astrophotography, such as capturing the Milky Way core, large nebulae, or rich star fields, this large image circle ensures that every corner of your image remains sharp and usable. There’s no need for external flatteners or additional correctors.
William Optics Internal Focus Design (WIFD)
The Ultra-Cat 108 uses a unique internal focusing mechanism called the William Optics Internal Focus Design (WIFD). Instead of relying on a traditional external drawtube focuser that moves in and out, WIFD adjusts the optics internally.
This approach offers several advantages:
- It eliminates drawtube sag or tilt when using heavy cameras.
- Focus remains stable and precise, even after rotating the telescope or slewing.
- It works seamlessly with electronic auto-focus systems (like the ZWO EAF), making remote imaging sessions more reliable.
- This system adds durability and enhances the overall rigidity of the telescope’s structure, critical for long-exposure photography.
Patented Handlebar Design
Portability and ease of handling are also considered. The Ultra-Cat 108 comes with a unique handlebar that makes transporting and mounting the telescope much easier.
The handle also doubles as a dovetail mount for attaching accessories like a guide scope or finder. This design ensures the telescope remains well-balanced, especially when fully loaded with imaging gear..
Full Specifications
- Optical Design: 5-element Petzval
- Glass Types: 2x Super ED, 1x ED, 1x Lanthanum, 1x X-Element
- Aperture: 108mm
- Focal Length: 518mm
- Focal Ratio: f/4.8
- Image Circle: 60mm
- Focuser: Internal WIFD rack-and-pinion, EAF-compatible
- Tube Length (Retracted): 512.9mm
- Tube Length (Extended): 617.9mm
- Weight: 7.82 kg
- Camera Compatibility: Medium Format, Full Frame, APS-C, MFT
Pricing and Availability
As of today, the Ultra-Cat 108 is available for preorder through authorized retailers and the official website. It is set to be shipped in 2025 Q1. It’s priced around USD 3,598, positioning it as a high-end but value-packed telescope for serious astrophotographers. They offer an early bird bundle promotion with a free 50mm guide scope with early orders, adding more value for customers looking to build a complete imaging setup.
Clear skies!
