Sky-Watcher Evostar 72ED .85x Reducer Field Flattener

Sky-Watcher EvoStar 72ED 0.85x Reducer/Field Flattener
Wide-Field Wonders Start Here: Faster Imaging, Flatter Fields, Better Results

If you’re imaging with the Sky-Watcher EvoStar 72ED and want to take your astrophoto results to the next level, the 0.85x Reducer/Field Flattener is an essential upgrade. Whether you’re a seasoned astrophotographer or just starting your journey beyond visual observing, this precision-matched accessory is designed to unlock the full potential of your refractor by optimizing both speed and field correction.

Designed Specifically for the EvoStar 72ED

Unlike generic flatteners or reducers, this 0.85x unit is engineered specifically for the optical characteristics of the Sky-Watcher EvoStar 72ED. That tailored design ensures ideal back focus, minimal aberrations, and edge-to-edge sharpness—particularly when paired with APS-C and smaller camera sensors.

While it can be used with full-frame cameras, users should expect noticeable vignetting. A flat field is maintained across a substantial portion of the sensor, but the outer edges will show light falloff that may require aggressive flat calibration or cropping. For best results, this reducer/flattener is optimized for APS-C, Micro Four Thirds, and other crop-sensor formats.

Flatten Your Field for Perfect Stars to the Edge

Even premium doublets like the EvoStar 72ED can exhibit star elongation or field curvature at the edges—especially with today’s larger camera sensors. This reducer’s integrated field flattener corrects that issue, delivering crisp, round stars across the entire usable field. The improvement is immediate and noticeable, especially in wide-field imaging of dense star fields or extended nebulae.

Clean stars aren’t just pleasing—they’re critical for image stacking, guiding, and post-processing. Beginners will appreciate the boost in image quality right away, while advanced imagers will benefit from the improved calibration and cleaner signal across their frames.

Reduce Focal Length and Boost Imaging Speed

By reducing your scope’s focal length from 420mm to 357mm, this 0.85x reducer effectively increases your field of view while making your optical system faster—f/5.9 compared to the native f/5.8. That bump in speed means shorter exposure times and more data collected over the course of a night.

It’s a perfect match for modern CMOS cameras and DSLRs, allowing you to gather more photons per frame and reach deeper with less total integration time. Whether you're capturing broadband RGB or diving into narrowband, faster optics make a difference—especially under light-polluted skies or during limited clear windows.

Simple Setup, Camera-Friendly Spacing

The reducer uses a standard M48 thread and provides the standard 55mm back focus that most imagers are familiar with. That makes it compatible with a wide range of imaging gear, from DSLR cameras (with the appropriate T-ring) to cooled astrophotography cameras with filter wheels or drawer systems.

Setup is refreshingly simple—no special adapters, collimation, or spacing guesswork. Just thread it into your EvoStar 72ED’s focuser, attach your imaging train with proper spacing, and you’re ready to capture.

What’s Included

• Sky-Watcher 0.85x Reducer/Field Flattener for EvoStar 72ED

• Threaded metal dust caps (M48)

• Setup and back focus guidance

Ideal For:

• Beginners wanting cleaner stars and shorter exposures with a simple, proven upgrade

• Intermediate imagers refining their portable rig for better wide-field results

• Advanced astrophotographers building a lightweight system with solid optics for wide-field nebulae, dark nebulae, and mosaics

Note: For full-frame users, this reducer can be used with cropping or well-calibrated flats, but it’s not a fully illuminated solution. APS-C and smaller sensors will get the best performance.

Summary:
The Sky-Watcher EvoStar 72ED 0.85x Reducer/Field Flattener is the imaging companion your telescope was designed for. Faster, flatter, and fine-tuned for your setup, it helps you get more out of every imaging session. Whether you're just starting out or building your travel-friendly wide-field rig, this is one upgrade that delivers immediate, visible results—especially for APS-C and crop sensor users.