The Explore Scientific 3" Field Flattener / 0.7x Focal Reducer is a high-performance dual-purpose accessory built for astrophotographers who want to maximize sharpness and minimize exposure times. Acting as both a field flattener and a focal reducer, it corrects curved focal planes and expands your field of view, allowing you to capture deeper, wider, and crisper celestial images.
As a field flattener, it eliminates edge-of-field distortions, turning star streaks into pinpoint dots — especially critical for full-frame and APS-C sensors. As a 0.7x reducer, it shortens your telescope’s focal length, delivering brighter images and a wider field of view — ideal for large nebulae, galaxies, and expansive star fields.
This precision-corrector is recommended for Explore Scientific 127mm and 152mm triplet refractors (not compatible with doublets). It includes an adapter for use with 2" rack-and-pinion focusers, while 2.5" HEX focuser users (standard on 127mm APOs) should add adapter #510366 for compatibility.
With a 55mm back focus requirement (52mm when using the included M42x0.75 adapter), it’s perfectly tailored to standard DSLR spacing with a T-ring or dedicated astro cameras.
CA Residents: Prop 65 WARNING(S)
⭐ Features & Benefits
- Dual-purpose optical system: Field flattener + 0.7x focal reducer
- Reduces focal ratio to speed up exposure and brighten deep-sky images
- Flattens curved fields for edge-to-edge sharpness on large sensors
- Fully multi-coated optics for high contrast and maximum light transmission
- Ideal for astrophotography with Explore Scientific APO triplets (127mm, 152mm)
- Includes adapter for 2" rack-and-pinion focusers
- Threaded for M42 and M48 T-rings and dedicated astro cameras
- Provides 55mm of back focus (52mm when M42 adapter is used)
🌟 Who It’s For
- Deep-sky astrophotographers using refractors with long focal lengths
- Users of Explore Scientific 127mm or 152mm triplet APO refractors
- Anyone seeking sharper star fields and shorter imaging times
🎯 What You’ll Be Able to Do
- Capture wide-field nebulae, galaxies, and clusters with sharper edges
- Reduce exposure times while maintaining image quality
- Achieve flat, professional-grade images across the sensor — even full-frame
🎒 What’s Included
- 3-inch Field Flattener / 0.7x Focal Reducer
- Threaded adapter for 2" rack-and-pinion focusers
-
M42x0.75 adapter for T-ring and camera compatibility
(Adapter #510366 required for 2.5" HEX focusers — sold separately)
Specs
| Item Number | FFFR507X-00 |
| Weight | 1.4 lb / 0.64 kg |
| Diameter | 78.3 mm |
| Height | 90.1 mm |
Warranty Information
This product is covered by a Limited One-Year USA Warranty, valid when registered within 60 days of purchase. To activate your warranty, please visit the Explore Scientific website and complete the registration form at: