Designed for stargazing and astrophotography, the Cat 51 WIFD 51mm f/4.9 Apochromatic Refractor Telescope from William Optics uses an unorthodox design for supporting heavy cameras and delivers a wide field, a fast focal ratio, and a Petzval lens for beautiful images. The WIFD (William Optic Internal Focus Design) places the 10:1 rack-and-pinion focuser in the center of the optical tube, eliminating the tilt and vignetting that can occur from heavy cameras on traditional rear-mounted focusers. A four-element Petzval-style lens yields a sharp image with no need for a flattener and the dust cover has a built-in Bahtinov mask for tack-sharp star images. This optical tube assembly requires a mount and a tripod for use.
Optical Tube Assembly
- Fast f/4.9 focal ratio and 250mm focal length for wide field of view and fast exposure times
- Apochromatic Petzval-style four-element lens produces rich views with minimal chromatic aberration
- Sharp image with no need for a separate field flattener
- Supports 48mm image circle for full-frame, APS-C, and micro four thirds cameras
- Dust cover with integrated Bahtinov mask allows for fine focusing on stars
- Built-in tilt adapter
- Camera angle rotation device
- M54 female thread for cameras, accessories, or eyepiece diagonals
Focuser
- William Optics Internal Focus Design places focuser in center of OTA to balance the weight of imaging systems
- Precise internal sliding of fixed optics prevents image shift, ensuring stable and clear observations
- 10:1 coarse and fine focus rack-and-pinion design
- Compatible with ZWO EAF automatic focuser
- 0-23mm focus travel, ruler to 30mm
- Dial-style thermometer for gauging temperature effect on optical tube
Use and Handling
- Anodized aluminum optical tube
- Sturdy mounting ring and handle assembly with 210mm Vixen-style dovetail
- Additional dovetail with thumbscrews on handle for guidescope or other accessory