William Optics SpaceCat 51 III WIFD f/4.9 Petzval Refractor Telescope
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- Limited Special Edition: Gray version of the Redcat 51 III - quantity limited to stock on hand
- 4-Element Petzval Optics: Delivers sharp, flat-field images from edge to edge
- 250mm Focal Length: Ideal for wide-field astrophotography
- Fast f/4.9 Optics: Captures bright, detailed images quickly
- WIFD Focuser: Provides precise internal focusing without extending the tube
- FPL-53 Glass: Minimizes chromatic aberration for accurate color
- Built-In Rotator: Makes framing quick and precise
- M48 Filter Thread: Accepts standard 2" filters
- 45mm Image Circle: Supports full-frame and APS-C cameras
The Latest Evolution of Best-Selling RedCat Series: 51 Gen III
What Makes the RedCat 51 Gen III a Standout
Built-In Filter Thread
Installing your filter is easy! Unscrew the included M48 adapter, thread in any standard M48 light pollution or specialty filter, and you’re ready to go.
This is especially handy for DSLR or mirrorless users—no need for clip-in filters. Just use any standard 2" filter across all your cameras, whether it's a dedicated astronomy camera or a regular digital camera.
Wide-Field Imaging
The 250mm focal length and f/4.9 of the RedCat 51 make it an ideal choice for wide-field astrophotography, allowing you to capture expansive views of nebulae, galaxy clusters, and large open star fields.
The RedCat 51 Gen III WIFD accommodates high-resolution cameras and heavier, cooled setups with ease, offering a versatile imaging experience with a design that ensures minimal vignetting on full-frame sensors.
Revolutionary WIFD
Unlike traditional focusers that extend out the back of the telescope, WIFD moves the optical elements inside the tube. This eliminates vignetting, prevents sensor tilt from the telescope itself, and provides rock-solid stability. With no external drawtube, there’s no risk of sag, even when using heavy accessories like a large filter wheel or DSLR camera.
Petzval Design for Next-Level Imaging
The RedCat 51 III uses a four-element Petzval design with premium FPL-53 glass to provide excellent color correction, minimize chromatic aberration, and produce sharp, round stars across its full 45mm image circle. The integrated flat-field design eliminates the cost, weight, and complexity of a separate field flattener while also removing strict backfocus-spacing requirements. Any imaging system measuring 68.2mm or less from the rear M54 threads can be brought into focus, making it easy to incorporate cameras, filter wheels, rotators, and other accessories.
Durability Meets Portability
Weighing just 3.9 lbs (1.77 kg), the RedCat 51 is easy to carry, easy to mount, and quick to set up. It's great for beginners who may be using portable tracking mounts like the Sky-Watcher Star Adventurer GTi, Star Adventurer 2i Pro, or iOptron SkyGuider. Because of its wide field of view, minor imperfections and distortions in star shape are less noticeable. This means you don’t need to track the night sky as precisely as you would if you were using longer focal lengths. Crafted from CNC-machined aluminum, the Cat 51 WIFD provides durability without sacrificing portability, ensuring it’s always ready for your next adventure under the stars.
All the Essentials Included
The William Optics RedCat 51 Gen III comes fully equipped, so you can start imaging right away! You’ll get a Bahtinov mask for quick and accurate focusing. The dual Vixen/Arca-Swiss mounting plate makes it easy to attach the telescope to your mount or many standard photo tripods. Plus, it includes a soft carry case, handlebar, lens cap, and a full Allen key set for quick adjustments. This saves you both time and money. You won’t need to hunt down extra parts. Just add your camera and mount, and you’re ready to capture the night sky!
Easily Connect Your Camera
The RedCat 51 Gen III WIFD works with a wide range of cameras, so you can build the setup that fits you best. It includes M54 x 0.75 and M48 x 0.75 threads for direct connection to most astronomy cameras and accessories. If you’re using a DSLR or mirrorless camera, just add a T-ring or T-mount for your camera brand, and you’re ready to go. Whether you shoot with a full-frame, APS-C, or dedicated astro camera, the RedCat 51 gives you the flexibility to start imaging right away.
Compatible with 1.25” Eyepieces
William Optics offers a 1.25" 90-degree diagonal (sold separately), allowing you to use the RedCat 51 with eyepieces for visual observing as well. Keep in mind that, depending on the back-focus requirements of your eyepiece, not all 1.25" eyepieces may reach focus. Also, this scope is not compatible with 2" diagonals or eyepieces.
Specifications
- Color: Limited Edition Space Grey
- Optical Design: Four-element Petzval
- Glass Type: FPL-53
- Aperture: 51 mm (2.0 in)
- Focal Length: 250 mm (9.8 in)
- Focal Ratio: f/4.9
- Image Circle: 48 mm (1.9 in)
- Compatible Camera Formats: Full-frame, APS-C, and Micro Four Thirds
- Focuser Type: William Optics Internal Focus Design (WIFD)
- Electronic Focuser Compatibility: ZWO EAF
- Focus Travel: 23 mm (0.9 in); scale marked to 30 mm (1.2 in)
- Specific Backfocus Required: No
- Field Flattener Required: No
- Included Adapters: Tilt adjuster, camera rotator, and M54-to-M48 adapter
- Tube Length: 298–346 mm (11.7–13.6 in)
- Dew Shield Diameter: 84 mm (3.3 in)
- Dew Shield Circumference: 265 mm (10.4 in)
- OTA Weight: 3.90 lb (1.77 kg)
- Weight with Rings, Dovetail, and Saddle: 5.25 lb (2.38 kg)
- Soft Case Exterior Dimensions: 15.4 x 9.8 x 10.6 in (39 x 25 x 27 cm)
Optical Test Charts
Works with ZWO EAF Right Out of the Box
The RedCat 51 WIFD arrives fully compatible with the ZWO EAF (electronic automatic focuser). Unlike previous models that required third-party adapters, this version makes it easier than ever to achieve perfect focus.
Best of all, installation is quick and hassle-free, saving you time, effort, and frustration. Here’s how:
- Remove the lock and tension screw from the focuser.
- On the focus knob without the fine adjustment, use a 2mm Allen key to remove the top screw.
Rotate the knob to locate two inner shaft screws inside the hole. Loosen these, but do not remove them completely. - Remove the focus knob.
- Align the EAF’s mounting bracket with the exposed screw hole and the nearby 2mm hole on the fine-tuning knob end, near where the lock and tension screw was removed.
- Align the EAF’s mounting bracket with the exposed screw hole and the 2mm hole on the fine-tune knob end (near where the lock and tension screw was).
- Use the two inner shaft screws to secure the EAF to the focuser shaft.
- Tighten both bracket screws to finish the installation.
Included Tilt Adapter for Better Imaging
The new RedCat 51 features an upgraded tilt adapter with M54 threads, offering improved performance for full-frame sensors and potentially reducing vignetting. This is a significant upgrade over the previous version. Plus, a standard M48 x 0.75 adapter is included, making it compatible with common imaging trains for even more flexibility.
RedCat 51 Anatomy
A. Rear Dust Cap (M48)
B. Saddle Handle Bar
C. WIFD Focuser
D. Dew Shield
E. Lens Cover with Bahtinov Mask
F. Front Bahtinov Mask Cover
G. Mounting Ring / Knob
H. Camera Angle Rotator
I. 210mm Dovetail Bar
J. Dual Speed 10:1 Ratio Focus Knob with Fine Focus Control
K. M4 Screw Holes for Finder Bracket
L. M4 Locking Screws on Saddle Handle Bar
M. Camera Angle Rotation Locking Screw
N. M4 Screw Holes for Finder Bracket
O. Focuser Adjusting Knob with Thermometer
P. M48 Adapter (for Camera Mount)
Other Information
- Country of Manufacture: Taiwan
The Latest Evolution of Best-Selling RedCat Series: 51 Gen III
What Makes the RedCat 51 Gen III a Standout
Built-In Filter Thread
Installing your filter is easy! Unscrew the included M48 adapter, thread in any standard M48 light pollution or specialty filter, and you’re ready to go.
This is especially handy for DSLR or mirrorless users—no need for clip-in filters. Just use any standard 2" filter across all your cameras, whether it's a dedicated astronomy camera or a regular digital camera.
Wide-Field Imaging
The 250mm focal length and f/4.9 of the RedCat 51 make it an ideal choice for wide-field astrophotography, allowing you to capture expansive views of nebulae, galaxy clusters, and large open star fields.
The RedCat 51 Gen III WIFD accommodates high-resolution cameras and heavier, cooled setups with ease, offering a versatile imaging experience with a design that ensures minimal vignetting on full-frame sensors.
Revolutionary WIFD
Unlike traditional focusers that extend out the back of the telescope, WIFD moves the optical elements inside the tube. This eliminates vignetting, prevents sensor tilt from the telescope itself, and provides rock-solid stability. With no external drawtube, there’s no risk of sag, even when using heavy accessories like a large filter wheel or DSLR camera.
Petzval Design for Next-Level Imaging
The RedCat 51 III uses a four-element Petzval design with premium FPL-53 glass to provide excellent color correction, minimize chromatic aberration, and produce sharp, round stars across its full 45mm image circle. The integrated flat-field design eliminates the cost, weight, and complexity of a separate field flattener while also removing strict backfocus-spacing requirements. Any imaging system measuring 68.2mm or less from the rear M54 threads can be brought into focus, making it easy to incorporate cameras, filter wheels, rotators, and other accessories.
Durability Meets Portability
Weighing just 3.9 lbs (1.77 kg), the RedCat 51 is easy to carry, easy to mount, and quick to set up. It's great for beginners who may be using portable tracking mounts like the Sky-Watcher Star Adventurer GTi, Star Adventurer 2i Pro, or iOptron SkyGuider. Because of its wide field of view, minor imperfections and distortions in star shape are less noticeable. This means you don’t need to track the night sky as precisely as you would if you were using longer focal lengths. Crafted from CNC-machined aluminum, the Cat 51 WIFD provides durability without sacrificing portability, ensuring it’s always ready for your next adventure under the stars.
All the Essentials Included
The William Optics RedCat 51 Gen III comes fully equipped, so you can start imaging right away! You’ll get a Bahtinov mask for quick and accurate focusing. The dual Vixen/Arca-Swiss mounting plate makes it easy to attach the telescope to your mount or many standard photo tripods. Plus, it includes a soft carry case, handlebar, lens cap, and a full Allen key set for quick adjustments. This saves you both time and money. You won’t need to hunt down extra parts. Just add your camera and mount, and you’re ready to capture the night sky!
Easily Connect Your Camera
The RedCat 51 Gen III WIFD works with a wide range of cameras, so you can build the setup that fits you best. It includes M54 x 0.75 and M48 x 0.75 threads for direct connection to most astronomy cameras and accessories. If you’re using a DSLR or mirrorless camera, just add a T-ring or T-mount for your camera brand, and you’re ready to go. Whether you shoot with a full-frame, APS-C, or dedicated astro camera, the RedCat 51 gives you the flexibility to start imaging right away.
Compatible with 1.25” Eyepieces
William Optics offers a 1.25" 90-degree diagonal (sold separately), allowing you to use the RedCat 51 with eyepieces for visual observing as well. Keep in mind that, depending on the back-focus requirements of your eyepiece, not all 1.25" eyepieces may reach focus. Also, this scope is not compatible with 2" diagonals or eyepieces.
Specifications
- Color: Limited Edition Space Grey
- Optical Design: Four-element Petzval
- Glass Type: FPL-53
- Aperture: 51 mm (2.0 in)
- Focal Length: 250 mm (9.8 in)
- Focal Ratio: f/4.9
- Image Circle: 48 mm (1.9 in)
- Compatible Camera Formats: Full-frame, APS-C, and Micro Four Thirds
- Focuser Type: William Optics Internal Focus Design (WIFD)
- Electronic Focuser Compatibility: ZWO EAF
- Focus Travel: 23 mm (0.9 in); scale marked to 30 mm (1.2 in)
- Specific Backfocus Required: No
- Field Flattener Required: No
- Included Adapters: Tilt adjuster, camera rotator, and M54-to-M48 adapter
- Tube Length: 298–346 mm (11.7–13.6 in)
- Dew Shield Diameter: 84 mm (3.3 in)
- Dew Shield Circumference: 265 mm (10.4 in)
- OTA Weight: 3.90 lb (1.77 kg)
- Weight with Rings, Dovetail, and Saddle: 5.25 lb (2.38 kg)
- Soft Case Exterior Dimensions: 15.4 x 9.8 x 10.6 in (39 x 25 x 27 cm)
Optical Test Charts
Works with ZWO EAF Right Out of the Box
The RedCat 51 WIFD arrives fully compatible with the ZWO EAF (electronic automatic focuser). Unlike previous models that required third-party adapters, this version makes it easier than ever to achieve perfect focus.
Best of all, installation is quick and hassle-free, saving you time, effort, and frustration. Here’s how:
- Remove the lock and tension screw from the focuser.
- On the focus knob without the fine adjustment, use a 2mm Allen key to remove the top screw.
Rotate the knob to locate two inner shaft screws inside the hole. Loosen these, but do not remove them completely. - Remove the focus knob.
- Align the EAF’s mounting bracket with the exposed screw hole and the nearby 2mm hole on the fine-tuning knob end, near where the lock and tension screw was removed.
- Align the EAF’s mounting bracket with the exposed screw hole and the 2mm hole on the fine-tune knob end (near where the lock and tension screw was).
- Use the two inner shaft screws to secure the EAF to the focuser shaft.
- Tighten both bracket screws to finish the installation.
Included Tilt Adapter for Better Imaging
The new RedCat 51 features an upgraded tilt adapter with M54 threads, offering improved performance for full-frame sensors and potentially reducing vignetting. This is a significant upgrade over the previous version. Plus, a standard M48 x 0.75 adapter is included, making it compatible with common imaging trains for even more flexibility.
RedCat 51 Anatomy
A. Rear Dust Cap (M48)
B. Saddle Handle Bar
C. WIFD Focuser
D. Dew Shield
E. Lens Cover with Bahtinov Mask
F. Front Bahtinov Mask Cover
G. Mounting Ring / Knob
H. Camera Angle Rotator
I. 210mm Dovetail Bar
J. Dual Speed 10:1 Ratio Focus Knob with Fine Focus Control
K. M4 Screw Holes for Finder Bracket
L. M4 Locking Screws on Saddle Handle Bar
M. Camera Angle Rotation Locking Screw
N. M4 Screw Holes for Finder Bracket
O. Focuser Adjusting Knob with Thermometer
P. M48 Adapter (for Camera Mount)
- Limited Special Edition: Gray version of the Redcat 51 III - quantity limited to stock on hand
- 4-Element Petzval Optics: Delivers sharp, flat-field images from edge to edge
- 250mm Focal Length: Ideal for wide-field astrophotography
- Fast f/4.9 Optics: Captures bright, detailed images quickly
- WIFD Focuser: Provides precise internal focusing without extending the tube
- FPL-53 Glass: Minimizes chromatic aberration for accurate color
- Built-In Rotator: Makes framing quick and precise
- M48 Filter Thread: Accepts standard 2" filters
- 45mm Image Circle: Supports full-frame and APS-C cameras
The Latest Evolution of Best-Selling RedCat Series: 51 Gen III
What Makes the RedCat 51 Gen III a Standout
Built-In Filter Thread
Installing your filter is easy! Unscrew the included M48 adapter, thread in any standard M48 light pollution or specialty filter, and you’re ready to go.
This is especially handy for DSLR or mirrorless users—no need for clip-in filters. Just use any standard 2" filter across all your cameras, whether it's a dedicated astronomy camera or a regular digital camera.
Wide-Field Imaging
The 250mm focal length and f/4.9 of the RedCat 51 make it an ideal choice for wide-field astrophotography, allowing you to capture expansive views of nebulae, galaxy clusters, and large open star fields.
The RedCat 51 Gen III WIFD accommodates high-resolution cameras and heavier, cooled setups with ease, offering a versatile imaging experience with a design that ensures minimal vignetting on full-frame sensors.
Revolutionary WIFD
Unlike traditional focusers that extend out the back of the telescope, WIFD moves the optical elements inside the tube. This eliminates vignetting, prevents sensor tilt from the telescope itself, and provides rock-solid stability. With no external drawtube, there’s no risk of sag, even when using heavy accessories like a large filter wheel or DSLR camera.
Petzval Design for Next-Level Imaging
The RedCat 51 III uses a four-element Petzval design with premium FPL-53 glass to provide excellent color correction, minimize chromatic aberration, and produce sharp, round stars across its full 45mm image circle. The integrated flat-field design eliminates the cost, weight, and complexity of a separate field flattener while also removing strict backfocus-spacing requirements. Any imaging system measuring 68.2mm or less from the rear M54 threads can be brought into focus, making it easy to incorporate cameras, filter wheels, rotators, and other accessories.
Durability Meets Portability
Weighing just 3.9 lbs (1.77 kg), the RedCat 51 is easy to carry, easy to mount, and quick to set up. It's great for beginners who may be using portable tracking mounts like the Sky-Watcher Star Adventurer GTi, Star Adventurer 2i Pro, or iOptron SkyGuider. Because of its wide field of view, minor imperfections and distortions in star shape are less noticeable. This means you don’t need to track the night sky as precisely as you would if you were using longer focal lengths. Crafted from CNC-machined aluminum, the Cat 51 WIFD provides durability without sacrificing portability, ensuring it’s always ready for your next adventure under the stars.
All the Essentials Included
The William Optics RedCat 51 Gen III comes fully equipped, so you can start imaging right away! You’ll get a Bahtinov mask for quick and accurate focusing. The dual Vixen/Arca-Swiss mounting plate makes it easy to attach the telescope to your mount or many standard photo tripods. Plus, it includes a soft carry case, handlebar, lens cap, and a full Allen key set for quick adjustments. This saves you both time and money. You won’t need to hunt down extra parts. Just add your camera and mount, and you’re ready to capture the night sky!
Easily Connect Your Camera
The RedCat 51 Gen III WIFD works with a wide range of cameras, so you can build the setup that fits you best. It includes M54 x 0.75 and M48 x 0.75 threads for direct connection to most astronomy cameras and accessories. If you’re using a DSLR or mirrorless camera, just add a T-ring or T-mount for your camera brand, and you’re ready to go. Whether you shoot with a full-frame, APS-C, or dedicated astro camera, the RedCat 51 gives you the flexibility to start imaging right away.
Compatible with 1.25” Eyepieces
William Optics offers a 1.25" 90-degree diagonal (sold separately), allowing you to use the RedCat 51 with eyepieces for visual observing as well. Keep in mind that, depending on the back-focus requirements of your eyepiece, not all 1.25" eyepieces may reach focus. Also, this scope is not compatible with 2" diagonals or eyepieces.
Specifications
- Color: Limited Edition Space Grey
- Optical Design: Four-element Petzval
- Glass Type: FPL-53
- Aperture: 51 mm (2.0 in)
- Focal Length: 250 mm (9.8 in)
- Focal Ratio: f/4.9
- Image Circle: 48 mm (1.9 in)
- Compatible Camera Formats: Full-frame, APS-C, and Micro Four Thirds
- Focuser Type: William Optics Internal Focus Design (WIFD)
- Electronic Focuser Compatibility: ZWO EAF
- Focus Travel: 23 mm (0.9 in); scale marked to 30 mm (1.2 in)
- Specific Backfocus Required: No
- Field Flattener Required: No
- Included Adapters: Tilt adjuster, camera rotator, and M54-to-M48 adapter
- Tube Length: 298–346 mm (11.7–13.6 in)
- Dew Shield Diameter: 84 mm (3.3 in)
- Dew Shield Circumference: 265 mm (10.4 in)
- OTA Weight: 3.90 lb (1.77 kg)
- Weight with Rings, Dovetail, and Saddle: 5.25 lb (2.38 kg)
- Soft Case Exterior Dimensions: 15.4 x 9.8 x 10.6 in (39 x 25 x 27 cm)
Optical Test Charts
Works with ZWO EAF Right Out of the Box
The RedCat 51 WIFD arrives fully compatible with the ZWO EAF (electronic automatic focuser). Unlike previous models that required third-party adapters, this version makes it easier than ever to achieve perfect focus.
Best of all, installation is quick and hassle-free, saving you time, effort, and frustration. Here’s how:
- Remove the lock and tension screw from the focuser.
- On the focus knob without the fine adjustment, use a 2mm Allen key to remove the top screw.
Rotate the knob to locate two inner shaft screws inside the hole. Loosen these, but do not remove them completely. - Remove the focus knob.
- Align the EAF’s mounting bracket with the exposed screw hole and the nearby 2mm hole on the fine-tuning knob end, near where the lock and tension screw was removed.
- Align the EAF’s mounting bracket with the exposed screw hole and the 2mm hole on the fine-tune knob end (near where the lock and tension screw was).
- Use the two inner shaft screws to secure the EAF to the focuser shaft.
- Tighten both bracket screws to finish the installation.
Included Tilt Adapter for Better Imaging
The new RedCat 51 features an upgraded tilt adapter with M54 threads, offering improved performance for full-frame sensors and potentially reducing vignetting. This is a significant upgrade over the previous version. Plus, a standard M48 x 0.75 adapter is included, making it compatible with common imaging trains for even more flexibility.
RedCat 51 Anatomy
A. Rear Dust Cap (M48)
B. Saddle Handle Bar
C. WIFD Focuser
D. Dew Shield
E. Lens Cover with Bahtinov Mask
F. Front Bahtinov Mask Cover
G. Mounting Ring / Knob
H. Camera Angle Rotator
I. 210mm Dovetail Bar
J. Dual Speed 10:1 Ratio Focus Knob with Fine Focus Control
K. M4 Screw Holes for Finder Bracket
L. M4 Locking Screws on Saddle Handle Bar
M. Camera Angle Rotation Locking Screw
N. M4 Screw Holes for Finder Bracket
O. Focuser Adjusting Knob with Thermometer
P. M48 Adapter (for Camera Mount)
Other Information
- Country of Manufacture: Taiwan
| Telescope Focal Length | Up to 300mm |
|---|
William Optics SpaceCat 51 III WIFD f/4.9 Petzval Refractor Telescope