Field Flatteners & Reducers

Flattener or Reducer?

• 1.0x flattener: Keeps native focal length. Best for small targets and when your camera's pixel scale already suits the telescope.
• 0.7x to 0.85x reducer-flattener: Wider field and faster focal ratio. A 0.8x reducer cuts exposure time by about a third.
• SCT reducers: f/6.3 reducer-corrector for standard SCTs, 0.7x reducer for EdgeHD.
• Dedicated or universal: A corrector designed for your exact telescope almost always beats a universal one, especially with larger sensors.

Getting the Back-Focus Right

Each corrector has a required distance to the sensor, often 55 mm but not always. Too short or too long and corner stars stretch. Plan the imaging train before ordering.

What We Confirm

• Model match: We confirm which corrector the manufacturer designed for your telescope and its focuser thread.
• Image circle: We check that the corrected field covers your sensor.
• Spacing: We give you the full list of spacers to reach the exact distance.

Flatteners and Reducers: Frequently Asked Questions

Does my telescope need a flattener?

Doublets and triplets used with anything larger than a small sensor almost always do. Petzval and quintuplet designs have one built in.

Can I use a flattener for visual observing?

It works but adds glass and back-focus. Most observers remove it for visual use.

My corner stars are still elongated. What now?

Send us a raw image. Stars pointing toward the centre mean spacing is too short; pointing away means too long.

Which corrector fits your telescope?

Send us your telescope model and camera. We will name the corrector and the spacing.