Celestron Reducer/Corrector – focal length reducer

Celestron Reducer/Corrector – focal length reducer

The Celestron Reducer/Corrector is a lens designed for Schmidt-Cassegrain telescopes, which shortens the focal length and corrects the field of view. With it, the same telescope can be used both as a long-focal-length telescope for observing the Moon and the planets, and as a fast, short-focal-length telescope for deep-sky objects and astrophotography. See also our other accessories for astronomical telescopes.

A wider field of view, both visually and when taking photographs

The lens reduces the focal length and the aperture ratio by 37 %, so an f/10 tube becomes f/6.3 and an f/11 tube becomes f/7. In visual observation, the same eyepiece provides lower magnification and a wider field of view. When taking photographs, the image area increases and exposure times are significantly reduced.

Installation and optional extras

The reducer/corrector is screwed onto the rear focus of the Schmidt-Cassegrain tube; on the C11 and C14 models, it is screwed onto the reducer plate. This can then be followed by, for example, a T-adapter, a 1.25-inch visual back, a zenith mirror or an off-axis guider. The fast aperture is also suitable for digiscoping terrestrial subjects in low light.

Structure and field curvature

The lens is housed in a machined, black anodised aluminium casing, and the internal surfaces have been blackened to reduce reflections. The textured surface provides a good grip for fitting and removal. The design reduces the field curvature typical of Schmidt-Cassegrain tubes, but does not eliminate it entirely.

Main features

• Converts a long-focal-length Schmidt-Cassegrain telescope into a fast, short-focal-length instrument.
• Two apertures in the same telescope, without compromising on image quality.
• Shorter exposure times and a wider field of view in astrophotography.
• Lower magnification and a wider field of view with the same eyepiece.
• Fully multi-coated optics transmit light efficiently and illuminate the field of view almost right to the edges.
• It is screwed directly onto the rear thread of the tube, after which the filming and observation equipment is attached to the rear of the lens.
• The plastic covers protect the lens from dust when it is not in use.

Technical specifications

• Focal length and aperture ratio reduction: 37 %
• Aperture ratio in an f/10 tube: f/6.3
• Aperture ratio in an f/11 tube: f/7
• Compatibility: Celestron Schmidt-Cassegrain telescopes
• Mounting: threaded connection to the SCT rear housing (C11 and C14: reducer plate)
• Coating: fully coated
• Body: machined aluminium, black anodised finish

View all Celestron products.