William Optics is well known for producing high-quality refractors that cater to astrophotographers seeking sharp optics in compact, travel-friendly designs. Among their diverse lineup, the Cat Series stands out as a collection of high-performance, small-aperture astrographs built specifically for deep-sky imaging. These telescopes feature petzval optical designs, premium glass elements, and exceptional build quality, making them favorites among astrophotographers worldwide. Each of these telescopes shares William Optics’ signature attention to detail, including CNC-machined bodies, robust focusers, and precision optics. In this article, we’ll explore the individual features of each model and see how they fit into an astrophotographer’s toolkit.
MiniCat 51: The Smallest Cat
The MiniCat 51 is the smallest telescope in the series, designed for portability without compromising optical quality. It is an ideal choice for astrophotographers looking for a lightweight, wide-field astrograph that can be used with star trackers or small equatorial mounts.
The petzval design ensures that the MiniCat 51 produces flat fields without requiring an additional field flattener, making it an easy plug-and-play option for wide-field imaging. The optics use FPL-53 and lanthanum glass, which helps minimize chromatic aberration. The built-in helical focuser ensures precise focusing, though it might not be as robust as a rack-and-pinion system for heavy imaging setups.
Specifications:
- Aperture: 51mm
- Focal Length: 250mm
- Focal Ratio: f/4.9
- Optical Design: Petzval quadruplet
- Weight: ~1.6 kg
Cat 51: The OG Cat
The Cat 51 is a slightly refined version of the MiniCat 51, retaining its core optical characteristics but improving some mechanical aspects. While it shares the same specifications, the build quality is slightly improved with better focus control. Additionally, the updated tube design enhances thermal stability, reducing focus drift.
Specifications:
- Aperture: 51mm
- Focal Length: 250mm
- Focal Ratio: f/4.9
- Optical Design: Petzval quadruplet
- Weight: ~1.8 kg
Cat 61: Stepping Up in Aperture and Focal Length
The Cat 61 offers a step up in aperture and focal length, making it a versatile option for those who want more resolution while keeping their setup lightweight and portable. With its 360mm focal length, the Cat 61 allows for more detailed imaging of nebulae and galaxies compared to the Cat 51. The optics remain excellent, providing a well-corrected, flat field for APS-C and full-frame sensors. The focuser is upgraded from the previous models, offering smoother and more precise control.
Specifications:
- Aperture: 61mm
- Focal Length: 360mm
- Focal Ratio: f/5.9
- Optical Design: Petzval quadruplet
- Weight: ~2.4 kg
Cat 71: The Professional-Grade Compact Astrograph
The Cat 71 is where the Cat Series transitions from compact astrographs to more serious imaging instruments. Its larger aperture, longer focal length, and refined mechanical features make it well-suited for deep-sky imaging. The Cat 71 is designed to work seamlessly with full-frame cameras, delivering sharp, well-corrected images across the entire field of view. The optical system ensures pinpoint stars with excellent color correction. The dual-speed focuser provides fine control, making it easier to achieve precise focus, even with heavy imaging setups.
Specifications:
- Aperture: 71mm
- Focal Length: 348mm
- Focal Ratio: f/4.9
- Optical Design: Petzval quadruplet
- Weight: ~3.2 kg
Cat 91: The Flagship Model for High-Resolution Imaging
At the top of the Cat Series is the Cat 91, offering the longest focal length and largest aperture in the lineup. This telescope is aimed at serious astrophotographers who need high resolution for capturing galaxies, nebulae, and clusters. The Cat 91 provides excellent image quality with a long focal length that allows astrophotographers to frame smaller deep-sky objects with more detail. Its robust build includes a high-quality dual-speed focuser and a rigid optical tube to ensure stability during long exposures.
Specifications:
- Aperture: 91mm
- Focal Length: 540mm
- Focal Ratio: f/5.9
- Optical Design: Petzval quadruplet
- Weight: ~4.7 kg
The William Optics Cat Series offers a range of high-quality, compact astrographs suited for different levels of astrophotography. Whether you’re a beginner looking for a lightweight, travel-friendly option or an experienced astrophotographer needing high-resolution imaging, there’s a Cat Series telescope to fit your needs. Each of these telescopes features premium optics, excellent mechanical quality, and a design optimized for astrophotography. Whether you’re imaging wide nebulae or distant galaxies, the William Optics Cat Series delivers exceptional results in a compact package.
Clear skies!
