Sky-Watcher Evostar 150DX .77x Reducer Field Flattener

Sky-Watcher EvoStar 150DX 0.77x Reducer/Field Flattener – Faster Imaging, Flatter Fields, and Expanded Potential for Your Refractor

If you're imaging with the Sky-Watcher EvoStar 150DX APO Refractor, you've already committed to exceptional optical quality. To bring out the very best in your imaging sessions, the 0.77x Reducer/Field Flattener is the ideal next step. Whether you're a beginner exploring deep sky targets or a seasoned astrophotographer optimizing your setup, this purpose-built accessory unlocks sharper stars, wider fields, and faster exposures—all designed specifically for the EvoStar 150DX.

Designed Specifically for the EvoStar 150DX

This reducer/flattener isn’t a generic solution. It’s been custom-engineered for the optical design of the Sky-Watcher EvoStar 150DX, eliminating the guesswork of spacing and correction. The built-in field flattener corrects field curvature and edge-of-frame aberrations, giving you sharp stars across a large, usable imaging area without trial-and-error tuning.

0.77x Reduction for Faster, Wider Imaging

The integrated reducer takes the EvoStar 150DX from f/8 to f/6.2, increasing your field of view and reducing your exposure times—by as much as 40%. This not only helps you gather more data in a single night, but also makes your mount and guiding setup more forgiving, especially for those just getting started in long-exposure imaging.

The shortened focal length (from 1200mm to roughly 924mm) makes this setup ideal for larger targets like nebulae and galaxies, while still delivering the resolution and contrast expected from a 6" APO.

34mm Image Circle – Optimized for APS-C Sensors

The reducer/flattener delivers a 34mm fully illuminated image circle, making it ideal for today's most popular APS-C sized sensors—commonly found in both DSLR and dedicated astro cameras. Cameras like the ZWO ASI2600MC Pro, QHY268M, Canon 90D, and Nikon D7500 will enjoy flat, well-corrected stars from corner to corner.

While it is compatible with full-frame cameras, users should be aware that the 34mm image circle won’t fully illuminate the entire 44mm diagonal of a full-frame sensor. If you’re using a camera like the Canon EOS 6D, Nikon D850, Sony A7 series, or ZWO ASI6200, expect some vignetting in the corners—which can be effectively corrected with proper flat frame calibration.

Camera Compatibility Made Simple

With a standard M48 thread and a 55mm backfocus requirement, this reducer makes it easy to integrate a wide variety of cameras using off-the-shelf spacers and adapters. Whether you're using a DSLR with a T-ring, a mirrorless body with a short backfocus adapter, or a cooled CMOS astro camera, the spacing is straightforward and beginner-friendly.

Precision Optics and Build Quality

This reducer/flattener features high-quality, fully multi-coated optics housed in a durable anodized aluminum body. The coatings maximize light transmission while reducing internal reflections and ghosting—keeping your stars tight and your background clean. The large 2.7" clear aperture minimizes vignetting and preserves image brightness, even with larger sensors.

Quick Specs:

• Designed For: Sky-Watcher EvoStar 150DX

• Reduction Factor: 0.77x (f/8 becomes f/6.2)

• Focal Length After Reduction: ~924mm

• Image Circle: 34mm (fully illuminated)

• Best For: APS-C sensors; usable with full-frame (some vignetting)

• Backfocus Requirement: 55mm

• Thread: M48 x 0.75

• Clear Aperture: 2.7" (68mm)

• Optics: Fully multi-coated

• Housing: CNC-machined, black anodized aluminum

Final Thoughts

The Sky-Watcher EvoStar 150DX 0.77x Reducer/Field Flattener is a must-have for anyone serious about imaging with the EvoStar 150DX. It offers a sharp, flat field over APS-C sensors, a generous image circle for full-frame use with flats, and a significant speed boost—all in a mechanically simple, optically matched package.

Whether you're shooting your first galaxy or building a full-frame narrowband rig, this accessory ensures your images start sharp and stay sharp—corner to corner.