William RedCat91 WIFD 91mm f/4.9 flatfield refractor for astrophotography

With the RedCat 91 WIFD astrograph, William offers a very well-corrected telescope for astrophotography up to full format.
 
 Aperture 91 mm / focal length 448 mm / focal ratio 1:4.9
 Petzval design with pure color apochromatic Super ED lens system
 Very well corrected and illuminated image field up to full format - the corrector is built in - no more adapter battle necessary
 Camera connection via the M48 external thread (suitable adapters are available) - working distance 55 mm
 360° rotation of the camera for the right image section
 Focusing via internal focusing (William Internal Focus Design - WIFD) like with telephoto lenses
 Tilting option for individual adjustment of the camera sensor to the telescope
 Prism rail for Vixen level prism clamps
 Bahtinov mask for astrophotography is included

William Optics RedCat 91mm f/4.9 WIFD Travel Apochromat and Astrograph
The William RedCat 51 is a successful model and has found its fans. It was supplemented by the more powerful sister models RedCat 61 and RedCat 71. William Optics now offers all of these telescopes with internal focusing; They are designed for mobile astrophotography and are carried by smaller mounts, sometimes even by stable star trackers.

The logical extension of these models is the RedCat 91 WIFD, which combines internal focusing with a particularly large opening. However, due to the weight of 6.3 kg, the mount should be a little more stable.

This apochromatic refractor is aimed at all astrophotographers and nature photographers who are looking for a portable and crisp telephoto lens. The 5-element Petzval design achieves a color-pure and fully corrected image field over 50 mm in diameter. The use of full-format cameras is even possible. Like many telephoto lenses, the focusing works internally, but like telescopes, it uses buttons with an additional fine focusing button.

The areas of application of the RedCat 91 Apo:
 Astrophotography: With a 448 mm focal length and fast f/4.9, short exposure times are possible. The working distance of 55 mm from the M48 thread enables the use of all common astro cameras, mirrorless system cameras and DSLR/SLR cameras. The fine focusing enables precise focusing, the rotation enables the selection of the appropriate image section. Included in delivery is a Bahtinov mask for astrophotography. The mask helps with focusing and is integrated into the lens attachment.
 Landscape photography and animal photography: The RedCat 91 is also ideal for photographing animals, for example. The internal focusing allows you to focus without shifting your weight, i.e. without changing your position. The image section is therefore retained. The imaging performance will impress you. A photo tripod is necessary for use.

Optical design: 5-element Petzval design with 3 Super ED elements
Opening: 91mm
Focal length: 448mm
Aperture ratio: f/4.9
Image field diameter: 50 mm diameter
Power at the star: The RMS radius of the central star point is 1.3 µm, the corners are 2.1 µm, ensuring razor-sharp images.
Flattener: Flat field lens design, no flattener required
Focusing: Internal focusing (William Internal Focus Design - WIFD), compatible with EAF
Fine focusing: 1/10 reduction
Focusing path: 0-35 mm (scale up to 40 mm)
Camera connection: M48x0.75 external thread, M54x0.75 external thread, M63 internal thread
Working distance from M48x0.75 thread: 55 mm back focus
Working distance from M54x0.75 thread: 64 mm back focus
360° rotation: yes
Tilter: yes, under rotation scale
Dew cap: integrated
Bahtinovmask: Yes
Viewfinder shoe: integrated into the handle
Mounting connection: Prism rail type Vixen
Length: 556mm
Weight: approx. 4.72 kg (OTA only), 6.3 kg (OTA with pipe clamps, prism rail and viewfinder shoe/handle)

 RedCat 91 WIFD travel apo
 Cover cap with Bahtinov mask
 M63-M54 adapter with cover cap
 M54-M48 adapter with cover cap
 Cover cap for fine focusing
 Pipe clamps with carrying handle
 Prism rail Vixen-Level, 290 mm long
 Carry bag