WILLIAM OPTICS REDCAT 91 WIFD f/4.9 REFRACTOR

The William Optics RedCat 91 WIFD is a new addition to WO's range of fast Petzval refractors with their innovative internal focusing mechanism. This makes it simple to install autofocusers such as the ZWO EAF without the need for clumsy belt-driven add-ons. It has a focuser bush diameter of 33mm and therefore it need the 33mm PLL adapter in order to connect the Prima Luce Lab Sesto Senso II focuser 

The RedCat 91 WIFD features the same excellent Petzval-type optics as the other Cats,  but delivers a large flat field with a 50mm image circle - perfect for full-frame and medium-format sensors. The Redcat 91 contains a combination of two Super ED, one ED and lanthanum lenses with full multi-coatings which produce sharp, vibrant images and excellent control of chromatic aberration.

Unlike typical refractors which require a separate field flattener and careful attention to backfocus distance, the Petzval optics in the RedCat 91 integrate these correcting lenses into the design with no need to calculate precise backfocus. As long as you're in focus, you're good to go!

The WIFD series has been designed from the ground up to support the latest large and heavy high-resolution cooled cameras and accessories. The focuser movement is integrated inside the main OTA, so no external focuser drawtube is needed. This will reduce tilt caused by focuser sag and mechanical flex and lessen vignetting.

WIFD focuser detail as found on the Redcat 61.

The focuser utilizes a zero image shift rack & pinion mechanism for precise adjustability of critical focus, with an external graduated display showing focus position. The lens cell is protected from the elements and is designed to not come out of alignment. The focuser is fully compatible with the ZWO EAF without the need for optional accessories.

With a fast focal ratio of f/4.9 and a focal length of 448mm, the RedCat 91 WIFD is perfect for capturing mid-sized deep space objects such as the Horsehead nebula, the Pleiades, Eta Carina and more. The RedCat also excels as a telephoto wildlife lens.

The CNC-machined and anodized handle bar with finder-style saddle is perfect for attaching a guide scope or other accessories. Like all William Optics telescopes, the lens cap includes a built-in Bahtinov mask to aid with manual focusing.

The built-in tilt adjuster makes it easy to correct image tilt without the need for disassembling the image train. M63 x 1, M54 x 0.75 and M48 x 0.75 threads are available to connect a wide variety of imaging systems. The M48 adapter includes an internal thread for fitting 2" filters. 

The RedCat 91 is compatible with the ZWO CAA but it will require to remove the screw with knob used to lock the telescope rotator and swap it with a grub screw M8-1.75 x 5mm.

Features

• Apochromatic lenses
• Anti-reflection multicoating
• Brand new patented integrated focuser design
  
• Super bright Bahtinov mask
• Vixen-style mounting plate
• Field rotator with markings for easy framing
  
• 48mm filter slot for standard 2" filters
• Finder-type saddle handlebar
• Modular mounting options
• Padded soft case included

Specifications

Included items

• RedCat 91 WIFD
  
• Patented Bahtinov mask
• Dew shield
• Vixen-style dovetail
• Finder-style handle bar saddle
• Camera angle rotator
• Internal tilt adapter
• Mounting rings
• Soft carry case

Instructions

Downloads

Instruction manual