# Best Field Flatteners for Edge-to-Edge Stars (2026) Source: https://stargazernest.com/best/field-flatteners Updated: 2026-09-15 Publisher: Stargazer Nest. Our score is an editorial rating out of 10 (fit 35%, features 25%, build 20%, value 20%), not a customer rating. Method: https://stargazernest.com/how-we-research#our-score Refractors focus a slightly curved field, so stars in the center look sharp while those at the frame edges bloat or stretch. A field flattener adds corrective elements to flatten that field across your sensor. Some models also act as focal reducers, shortening focal length for a wider, faster field. The critical spec is back-focus, the exact distance from the flattener to the sensor, which must be set precisely with spacers, along with matching the flattener to your scope's aperture and focal ratio. Flatteners suit refractor imagers using larger APS-C or full-frame sensors, where field curvature is most visible at the corners. A practical tip: confirm the required back-focus distance for your specific flattener, usually around 55mm, and measure your camera and adapter stack carefully. Getting spacing wrong by even a couple of millimeters leaves the corners misshapen, so dial it in with test frames before a full imaging run. ## Picks ### 1. SVBONY SV193 Focal Reducer 2 Inch 0.8X Field Flattener for SV503 80mm F7 ED Telescope Our score: 8.4/10 (Fit for the job 9/10 · Features and specs 8/10 · Build and materials 8/10 · Value 8/10) SVBONY SV193 2 Inch 0.8X focal reducer and field flattener designed for the SV503 80mm F7 ED telescope. Pros: - 0.8X reduction speeds up imaging while flattening the field - Designed specifically for the SV503 80mm F7 ED for correct spacing - 2 Inch format supports larger camera sensors Cons: - Optimized for one telescope, so results on others may vary - Requires correct back focus spacing to avoid elongated stars Details: https://stargazernest.com/product/B094QSGPPN ### 2. SVBONY SV193 Focal Reducer and Field Flattener M54x0.75 0.8X for SV503 70mm F6 ED Refractors Our score: 8.4/10 (Fit for the job 9/10 · Features and specs 8/10 · Build and materials 8/10 · Value 8/10) SVBONY SV193 focal reducer and field flattener with M54x0.75 thread and 0.8X for SV503 70mm F6 ED refractors. Pros: - Matched to SV503 70mm F6 ED refractors for flat, round stars - 0.8X reduction widens the field for large nebulae - M54x0.75 thread offers a secure connection to camera adapters Cons: - Specific thread and telescope match limits compatibility - Spacers may be needed to achieve proper back focus Details: https://stargazernest.com/product/B095CFYXQP ### 3. SVBONY SV209 Field Flattener 0.8X Focal Reducer for SV550 122mm APO Refractor Telescope Our score: 8.4/10 (Fit for the job 9/10 · Features and specs 8/10 · Build and materials 8/10 · Value 8/10) SVBONY SV209 0.8X field flattener and focal reducer for the SV550 122mm APO refractor telescope. Pros: - Designed for the SV550 122mm APO for optimal field correction - 0.8X reduction speeds exposures and enlarges the field - Helps large sensors capture sharp stars to the edges Cons: - Only suitable for the SV550 122mm refractor - Premium add-on cost for an already expensive telescope Details: https://stargazernest.com/product/B0CBJHTD4W ### 4. William Optics 2 inch 0.8x Adjustable Reducer / Field Flattener 4 Our score: 8.4/10 (Fit for the job 9/10 · Features and specs 8/10 · Build and materials 9/10 · Value 7/10) William Optics 2 inch 0.8x adjustable reducer and field flattener 4 for refractor astrophotography. Pros: - Adjustable design lets you tune spacing for different refractors - 0.8x reduction widens the field and shortens exposures - William Optics quality is known for solid machining Cons: - Adjustment requires trial and error to find the best setting - Premium price compared with dedicated fixed flatteners Details: https://stargazernest.com/product/B00CRLL46E ### 5. Celestron Focal Reducer and Field Corrector f/10 to f/6.3 for Schmidt-Cassegrain Telescopes Our score: 8.4/10 (Fit for the job 9/10 · Features and specs 8/10 · Build and materials 8/10 · Value 8/10) Celestron focal reducer and field corrector taking Schmidt-Cassegrain telescopes from f/10 to f/6.3. Pros: - f/10 to f/6.3 reduction widens the field and brightens images - Field corrector flattens stars for better SCT astrophotography - Official Celestron accessory widely used with SCTs Cons: - Only suitable for Schmidt-Cassegrain telescopes - Can show vignetting on larger camera sensors Details: https://stargazernest.com/product/B00009XVHZ ### 6. SVBONY SV193 Focal Reducer M54X1 Field Flattener for SV503 102mm ED Telescope Our score: 7.8/10 (Fit for the job 8/10 · Features and specs 7/10 · Build and materials 8/10 · Value 8/10) SVBONY SV193 focal reducer and field flattener with M54X1 thread for the SV503 102mm ED telescope. Pros: - Matched to the SV503 102mm ED for correct optical design - Flattens field curvature for sharp stars across the frame - M54X1 thread gives a secure, tilt-free attachment to the focuser Cons: - Check the reduction factor specs to confirm fit with your setup - Limited to the SV503 102mm telescope, so it will not move with you to a new scope Details: https://stargazernest.com/product/B095CFTPDX ### 7. Astromania Focal Reducer F/6.3 for Telescope SCT Standard Thread Multi Coated Field Corrector Our score: 7.8/10 (Fit for the job 8/10 · Features and specs 7/10 · Build and materials 7/10 · Value 9/10) Astromania F/6.3 focal reducer with SCT standard thread and multi coated field corrector for telescopes. Pros: - F/6.3 reduction makes SCTs faster for imaging and wider for viewing - SCT standard thread fits most Schmidt-Cassegrain telescopes - Budget alternative to branded focal reducers Cons: - Optical quality may not match Celestron or Meade reducers - Limited to SCT telescopes only, refractors and Newtonians need other correctors Details: https://stargazernest.com/product/B08B4LRJ73 As an Amazon Associate I earn from qualifying purchases.