William Optics

RedCat 61 WIFD f/4.9 Petzval APO


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  • Regular price $1,598.00

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Introducing the WILLIAM OPTICS Internal Focus Design (WIFD) Apochromatic Series.

This innovative and revolutionary design combines a precision (Patented) internal focusing mechanism with the highest quality optics available, providing the ultimate Apochromatic refractor for astrophotography.

Designed from the ground up with the ability to handle the newest generation of large, heavy, high-resolution cooled cameras, the rock-solid optical tube assembly is uncompromised in quality. The movement of the focuser is integrated inside the main tube assembly, so there are no movements of a focuser drawtube visible from the outside.  Enjoy the benefits of a traditional two speed fine focuser, while not worrying about limitations typically found in traditional rear mounted focusers.

Optically Unbeatable
  • Petzval air-spaced objective (FPL-53) in adjustable CNC machined ultra high precision lens cell.
  • Extremely sharp.
  • Excellent color correction.
  • Each lens is Fully Multi-Coated with a special super-high transmission coating (STM Coating) on all surfaces.
  • This F/4.9 lens is ideal for astrophotography.


Internal Focuser

NEW internal focuser.  Our new design includes the Patented WO center focuser with precise internal sliding of fixed optics to prevent image shift. 

The integrated position viewing window on the focuser provides instant verification of the graduated numerical display.  The smooth rack and pinion design is incorporated into the focuser to provide super fine adjustability for critical focus.  The internal movement of the optical elements is protected from the elements and can’t come out of alignment.

CAT Design

Improved “CAT” design ring tubes and dovetail base are lighter while remaining equally rigid. The new design allows for better balance with heavy accessories, and has integral placement of the focuser knobs, providing easy access to focusing during imaging.

Super Smooth Field Rotator

Our field rotator design features smooth camera rotation with markings for degrees and a locking thumbscrew to prevent accidental camera movement.

Attention to Details

Though you will never need it, you have a 2-year warranty from WO, and the certainty that we will be there to assist you even beyond that, if you need!



    61 mm (2.4")

    Focal Length

    300 mm

    Focal Ratio


    Glass Type


    Optical Design


    Tube Weight

    5.43 lbs (2.4kg)

    Tube Length


    Dew Shield Outer Diameter (for Solar Filter)
    • William Optics WIFD RedCat 61mm f/4.9 Apo Refractor OTA
    • Mounting Rings
    • CNC Carry Handle Bar
    • Dovetail Plate
    • Innovative Bahtinov Mask Cover (Patented)
    • Soft Carry Case

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