Field Flatteners & Correctors

Field flatteners, coma correctors and reducers

Field flatteners and correctors are the optical accessories that turn good astrophotos into sharp ones, right out to the corners of the frame. Many telescopes focus starlight onto a slightly curved field, so edge stars look stretched, and a field flattener corrects that curve so every star is a tight point.

This collection brings together flatteners, coma correctors, and reducer-flatteners that add a wider, faster field. A refractor with elongated corner stars usually needs a field flattener; a fast Newtonian needs a coma corrector. Each listing notes the scopes and thread sizes it fits, because correct spacing is what makes a corrector work.

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Frequently asked questions

What does a field flattener do?

A field flattener corrects the curved focal plane of a telescope so stars stay sharp all the way to the edges of your camera frame, instead of appearing stretched or bloated in the corners.

What is the difference between a field flattener and a coma corrector?

A field flattener flattens a curved field, mainly on refractors, while a coma corrector removes the comet-shaped star flaring produced by fast Newtonian reflectors. Some reducer-flatteners also shorten focal length.

Do I need a field flattener for astrophotography?

If your stars look elongated toward the edges of the frame, yes. For wide-field imaging through a refractor a field flattener is usually essential; visual observers generally don't need one.