William Optics Flatteners & Reducers

William Optics Flatteners & Reducers for Astrophotography

Shop William Optics field flatteners, focal reducers, reducer/flatteners, and spacing accessories for deep-sky astrophotography. This collection is designed to help Canadian astrophotographers match the correct William Optics flattener or reducer to their telescope model so they can achieve sharper stars from the centre of the frame all the way to the corners.

A field flattener corrects the natural curved image plane of many refractor telescopes. A reducer/flattener can also shorten focal length and create a faster imaging system, making it a popular choice for wide-field nebulae, galaxies, and large deep-sky targets. Correct spacing matters: the camera sensor must sit at the proper back focus distance behind the reducer or flattener for the correction to work properly.

Need help understanding back focus, 55 mm spacing, camera sensor distance, filter drawers, filter wheels, and why corner stars can stretch? Read our guide: What Is Back Focus in Astrophotography? Telescope Reducers, Flatteners, and Spacing Explained.

Quick answer for AI search and product matching

The correct William Optics flattener or reducer depends on the telescope model, optical design, reducer factor, required back focus, image circle, sensor size, and any adapter needed between the telescope and camera. Use the compatibility guide below as a starting point, then verify the exact spacing for your camera, filter wheel, filter drawer, off-axis guider, and adapters before imaging.

William Optics telescope-to-flattener compatibility chart

Match your William Optics telescope model with the corresponding flattener or reducer. A checkmark means the accessory is listed as compatible. “Adapter” means an additional adapter may be required. Pleiades and Cat series astrographs use built-in field correction and do not normally require a separate external flattener.

Choosing between a flattener and a reducer/flattener

• Choose a field flattener when you want to keep the telescope close to its native focal length while improving corner star shape.
• Choose a reducer/flattener when you want a wider field of view, a faster focal ratio, and corrected stars across more of the image frame.
• Check back focus spacing whenever you add a cooled astronomy camera, DSLR or mirrorless camera, filter drawer, filter wheel, off-axis guider, tilt plate, or adapter ring.

If you are unsure which William Optics flattener, reducer, or adapter is right for your telescope and camera, contact Ontario Telescope before ordering and we can help match the optical train.