Explore Scientific 3" Field Flattener .7x Focal Reducer

The Explore Scientific 3" Field Flattener / 0.7x Focal Reducer is a dual-function optical corrector that both flattens the field and reduces focal length by 0.7x — two corrections in a single accessory. Designed for the larger Explore Scientific 127mm and 152mm triplet refractors, the 3" barrel provides a wider clear aperture than 2" correctors, reducing vignetting on larger camera sensors.

The 0.7x reduction is more aggressive than the standard 0.8x reducer, delivering wider fields of view and faster f/ratios. An f/8 refractor becomes f/5.6 — a significant speed increase that cuts required exposure times substantially. Fully multi-coated optics maintain contrast and light transmission through the optical path.

Includes a 3" nosepiece and M42x0.75 adapter for standard T-ring camera connections. Back-focus distance is 55mm from the rear flange. For 2" focuser users, the 2" Adapter for FFFR507X-00 is available separately.

Key Features

• Dual-function: field flattener + 0.7x focal reducer in one unit
• 3" barrel — larger clear aperture than 2" correctors for reduced vignetting
• Fully multi-coated optics
• 55mm back-focus standard
• Includes 3" nosepiece and M42x0.75 T-thread adapter

Compatible Telescopes

• ES 127mm refractors: ED127, FCD100-127 (triplet APO/ED designs)
• ES 152mm refractors: ED152, FCD100-152 (triplet APO/ED designs)
• Focal ratio range: f/7.5 to f/8 (tested and confirmed for both)
• Not compatible with: Doublet refractors

Ideal For

• Deep-sky astrophotographers — the 0.7x reduction and field flattening deliver wide, flat fields from premium refractors
• Large-sensor imaging — the 3" barrel passes a wider light cone than 2" correctors, reducing edge vignetting on APS-C and full-frame sensors