William Optics Tilt Xterminator STX launches

Posted on Tuesday, March 18, 2025 by RICHARD HARRIS, Executive Editor

William Optics recently introduced the Sensor Tilt Xterminator (STX), a sensor tilt adjustment aimed at providing astrophotographers with a faster, more precise, and user-friendly solution for achieving optimal optical alignment. The STX enhances traditional sensor tilt adjusters by offering a streamlined design that eliminates the need for disassembly. Unlike conventional systems that require camera removal for tilt correction, the STX allows adjustments to be made directly from the side of the assembly, significantly reducing setup time and enhancing ease of use.

New tilt adjustment system from William Optics: The Sensor Tilt Xterminator (STX)

By refining the original 4 pull-in and 8 push-out screw configuration into a more efficient 4 push-out and 4 lock screw system, the STX enables precise and controlled adjustments. This mechanism operates like a seesaw, allowing effortless corrections by loosening one screw and tightening the opposite diagonal screw to achieve fine tilt alignment. This design ensures that astrophotographers can make on-the-fly refinements without disrupting their imaging workflow, maintaining pinpoint star performance across the entire frame.


The Ultra-Cat 108 release timeline has been extended beyond the original launch date

William Optics is integrating this adjustment system into the Ultra-Cat 108, however, to ensure every unit meets their exacting quality requirements, the Ultra-Cat 108 release timeline has been extended beyond the original launch date. While understanding the anticipation surrounding the Ultra-Cat 108, William Optics prioritizes delivering an uncompromising astrophotography experience. They appreciate customers' patience and support as they finalize production and encourage staying tuned for further updates.


What is the William Optics Cat Series?

The Cat Series by William Optics consists of compact refractor telescopes designed for astrophotography. These telescopes use a Petzval optical design, which includes multiple lens elements to eliminate the need for additional field flatteners. This results in a flat field across the entire image sensor, making them particularly useful for capturing wide-field astrophotography images without distortion.

Each model in the series features extra-low dispersion (ED) glass to reduce chromatic aberration and improve image clarity. A built-in Bahtinov mask is integrated into the lens cap to assist with precise focusing, a necessary feature for astrophotographers.

A key innovation across newer models is the William Optics Internal Focus Design (WIFD). Instead of an external focuser that moves the optical tube, WIFD keeps the entire lens assembly fixed, moving elements internally. This prevents flexure, especially when using heavy cameras and accessories, and minimizes dust intrusion into the optical path.

  • Petzval Optical Design: Ensures a flat field without additional field flatteners.
  • ED Glass Elements: Reduces chromatic aberration, improving color accuracy and contrast.
  • Bahtinov Mask Integrated in Lens Cap: Helps users achieve precise focus without needing separate focusing tools.
  • WIFD (Internal Focus System): Eliminates focuser flexure, improves weight balance, and keeps the optical path dust-free.
  • Portable and Lightweight: Designed for easy transport and setup, making them suitable for field use.
     

Cat Series models

Each model varies in aperture, focal length, and imaging capability, providing different options based on user needs:

MiniCat 51 WIFD

  • Optics: 6-element Petzval design with 2 Super ED glass elements.
  • Aperture: 51mm
  • Focal Length: 178mm
  • Focal Ratio: f/3.5
  • Field of View: 14 degrees
  • Ideal For: Wide-field astrophotography with APS-C and full-frame cameras. The extremely fast f/3.5 focal ratio allows short exposure times while maintaining image sharpness.
     

Cat 51 WIFD

  • Optics: 4-element Petzval design.
  • Aperture: 51mm
  • Focal Length: 250mm
  • Focal Ratio: f/4.9
  • Ideal For: Astrophotographers needing a portable, wide-field scope with sharp stars across an APS-C or full-frame sensor.
     

Cat 61 WIFD

  • Optics: 4-element Petzval design.
  • Aperture: 61mm
  • Focal Length: 300mm
  • Focal Ratio: f/4.9
  • Ideal For: A step up in focal length from the Cat 51, offering better resolution while maintaining a compact form. Suitable for full-frame and APS-C cameras.
     

Cat 71 WIFD

  • Optics: 4-element Petzval design.
  • Aperture: 71mm
  • Focal Length: 350mm
  • Focal Ratio: f/4.9
  • Ideal For: Full-frame imaging with more light-gathering capability than the smaller models. Works well for deep-sky objects while retaining a wide field of view.
     

Cat 91 WIFD

  • Optics: 5-element Petzval design with 3 Super ED glass elements.
  • Aperture: 91mm
  • Focal Length: 448mm
  • Focal Ratio: f/4.9
  • Ideal For: Medium-format astrophotography, providing a larger image circle with pinpoint stars across the frame. The 91mm aperture gathers significantly more light than smaller models, making it ideal for faint deep-sky objects.
     

Ultra-Cat 108 (Preorder - Delayed Release)

  • Optics: Advanced 5-element Petzval design.
  • Aperture: 108mm
  • Focal Length: TBA
  • Focal Ratio: TBA
  • Status: Originally set for release, but delayed due to extended production time to meet quality standards.
  • Ideal For: High-end astrophotographers looking for the next level in performance with a larger aperture and a fully corrected imaging circle.
     

The William Optics Cat Series provides a range of Petzval refractors optimized for astrophotography. The design ensures minimal image distortion and high optical quality, with the added convenience of internal focusing and integrated focusing aids. Each model offers a balance of portability and performance, making them a solid choice for astrophotographers looking for high-quality imaging without complex setup requirements.

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