William Optics Mini Cat 51mm Ultra-Portable Astrograph

Description

William Optics Mini Cat 51mm Ultra-Portable Astrograph

The William Optics Mini Cat 51 Astrograph is built for astrophotography's who want wide-field images without the bulk of a traditional telescope. Compact, fast, and optically refined, it’s designed to capture large areas of the night sky—think nebulae, star fields, and comets—with impressive efficiency.

Fast Optics for Shorter Imaging Sessions

One of the most important specs here is the f/3.5 focal ratio. In practical terms, this allows significantly more light to reach your camera sensor compared to slower systems (like f/5). That translates to:

• Shorter exposure times
• Faster data collection during limited clear skies
• Better performance when imaging faint deep-sky objects

If you’re shooting targets like emission nebulae or wide Milky Way regions, this speed is a major advantage.

Wide-Field Imaging with Strong Optical Control

The Mini Cat uses a 178mm focal length, making it ideal for wide-field astrophotography. You can comfortably frame large celestial objects without mosaics.

Its 6-element Petzval optical design includes:

• 2 Super ED elements for reducing chromatic aberration
• Lanthanum glass for improved contrast and color correction

The result is sharp stars and accurate color across most of the frame—especially when paired with APS-C sensors. Full-frame cameras are supported, though edge performance may require some correction during post-processing.

Precision Focusing Without Mechanical Compromise

A common issue in astrophotography setups is image tilt caused by traditional focusing mechanisms. The Mini Cat addresses this with a patented internal focusing system (WIFD).

Instead of moving a drawtube, the system adjusts internal lens elements, which provides:

• Better optical alignment
• Reduced risk of tilt or flex
• Smooth, repeatable focusing

It’s also compatible with motorized focusers like the ZWO EAF, making it suitable for automated imaging setups.

Built for Portability

As the name suggests, portability is a core strength. The Mini Cat 51 is lightweight and compact enough to:

• Travel easily with small mounts
• Fit into grab-and-go astrophotography kits
• Pair well with portable tracking mounts

Despite its size, it doesn’t compromise on optical performance, making it a practical option for both backyard setups and dark-sky trips.

Real-World Use

This astrograph excels in:

• Wide-field nebula imaging
• Milky Way photography
• Comet tracking
• Large star clusters

It’s less suited for high-magnification planetary imaging, where longer focal lengths are required.

Who is this product for?

The Mini Cat 51 is ideal for:

• Astrophotography's focused on wide-field imaging
• Traveling astronomers needing lightweight gear
• Intermediate users upgrading from camera lenses
• Advanced users looking for a fast, portable secondary setup

If your goal is capturing expansive sky scenes quickly and efficiently, this telescope is purpose-built for that role.

What’s in the box

• William Optics Mini Cat 51 optical tube
• Mounting hardware (dovetail/base)
• Integrated handle
• Soft carrying case
• Documentation

Note: Guide scope and additional accessories (such as the 32mm Unguided) are sold separately.

Final Thoughts

The Mini Cat 51 stands out by combining very fast optics (f/3.5) with a compact, travel-friendly design and a mechanically robust focusing system. It’s not trying to be an all-purpose telescope—instead, it focuses on doing one job extremely well: capturing wide, detailed images of the night sky with minimal effort and time.

Features of the William Optics MiniCat 51mm Ultra-Portable Astrograph

• Ultra-compact 51mm apochromatic astrograph designed specifically for wide-field astrophotography
• Advanced 6-element Petzval optical design for sharp stars across the field without requiring an additional field flattener
• Fast f/3.5 focal ratio dramatically reduces exposure times and improves efficiency for capturing faint nebulae and large deep-sky targets
• 178mm focal length ideal for ultra-wide-field astrophotography and large celestial objects such as the North America Nebula, Rho Ophiuchi, Orion complex, and Milky Way star fields
• Premium optical system incorporates 2 Super ED elements and lanthanum glass to minimize chromatic aberration and improve color correction
• Fully multi-coated optics maximize light transmission and contrast while reducing internal reflections
• Petzval configuration delivers a naturally flat imaging field with no separate flattener needed
• Supports Full Frame, APS-C, and Micro Four Thirds cameras for versatile imaging compatibility Large 43.2mm image circle accommodates modern large-format imaging sensors
• Built-in WIFD rack-and-pinion focuser provides smooth and highly precise focusing performance
• Dual-speed 1:10 micro-focus system allows extremely fine focus adjustments for critical astrophotography applications
• Short focuser travel improves rigidity and helps maintain stable camera positioning during imaging sessions
• Built-in sensor tilt adjuster allows precise correction of camera tilt for improved corner star performance
• Integrated Camera Angle Adjuster (CAA) enables easy framing and image rotation without disturbing focus
• M54 to M48 adapter included for convenient connection to many astronomy cameras and accessories
• Rear M48 filter thread supports direct installation of standard 2-inch filters
• Compact tube length of only 210mm makes the MiniCat exceptionally portable and travel-friendlyLightweight optical tube assembly weighs approximately 1.67kg, helping reduce mount load requirements
• Total system weight of only about 2.29kg makes it ideal for airline travel and portable imaging setups
• Retractable dew shield helps reduce dew formation and minimizes storage size
• Integrated Bahtinov mask built into the lens cover enables quick and highly accurate focusing in the field
• Precision CNC-machined aluminum construction ensures excellent durability and premium finish quality
• Dual-purpose design can also function as a high-end photographic telephoto lens for landscape and daytime photography
• Compatible with electronic automatic focusers (EAF) for remote or automated imaging setups
• Includes dual-side dovetail plate compatible with both Vixen-style and Arca-Swiss mounting systems
• Supplied mounting ring and handlebar provide convenient transport and accessory attachment options
• Optimized for modern CMOS astronomy cameras and portable star tracker systems
• Excellent choice for beginners entering astrophotography as well as experienced wide-field imagers
• Fast optical speed allows shorter sub-exposures and improved imaging productivity under limited clear skies
• Wide field of view makes the telescope highly suitable for capturing large nebulae, comet tails, Milky Way panoramas, and constellation regions
• Telescope-grade APO optics deliver sharper stars and more accurate color reproduction than many conventional camera lenses
• Designed to achieve focus flexibility across a range of imaging configurations thanks to the Petzval optical system
• Soft carrying case included for safe storage and easy transport
• Includes Allen key set and essential adapters for straightforward setup out of the box
• Elegant cat-inspired industrial design continues the famous William Optics “Cat” astrograph series aesthetic
• Suitable for portable astrophotography rigs, travel astronomy, and lightweight equatorial mounts
• Excellent match for one-shot color CMOS cameras commonly used in modern astrophotography
• Ideal for capturing expansive night-sky compositions with minimal setup complexity
• Wide-field focal length helps simplify tracking requirements compared to longer focal length telescopes
• Precision mechanical components engineered for imaging stability and repeatable performance
• Designed and manufactured by William Optics, a globally recognized premium astronomy brand

Click the following link to explore amazing deep-sky photographs taken with the William Optics MiniCat 51mm Astrograph.
Telescopes & lenses - AstroBin