Sky-Watcher Esprit 120 .77x Reducer Field Flattener

Sky-Watcher Esprit 120 0.77x Reducer/Field Flattener – Speed, Precision, and Optical Harmony

The Sky-Watcher 0.77x Reducer/Field Flattener is engineered specifically for the Esprit 120 ED Triplet refractor, transforming an already premium optical tube into a wide-field imaging powerhouse. Designed to reduce focal length, flatten the field, and maintain tight star profiles across its corrected image circle, this accessory gives you faster exposures, wider framing, and precision performance without the guesswork.

Whether you're just stepping into the world of astrophotography or you're a seasoned imager fine-tuning your rig, this reducer/flattener helps you extract the most from your Esprit 120.

Optimized for the Esprit 120 – Not a Generic Glass Stack

This isn't a one-size-fits-all corrector. The Sky-Watcher 0.77x Reducer is optically matched to the Esprit 120's native f/7 triplet lens system. It compensates for field curvature while preserving the Esprit’s renowned color correction and high-contrast imaging capabilities. The result? Clean, sharp stars across an APS-C frame without added chromatic aberration or edge distortion.

The reducer brings the Esprit’s focal length down from 840mm to 646.8mm, converting it to a fast f/5.4 system—ideal for capturing large nebulae, rich star fields, and extended galaxies. It’s a big performance boost with minimal setup complexity.

34mm Image Circle – Ideal for APS-C Sensors

This reducer delivers a corrected field with a 34mm image circle, which provides full-frame coverage for APS-C sensors (like the ASI2600MC/MM, Nikon D5600, or Canon 90D). It will physically illuminate full-frame sensors, but users should expect vignetting and some off-axis aberrations beyond the corrected field. Flat frames and careful framing can mitigate this for partial full-frame use, but for best results, stick with APS-C or smaller sensors.

Integration and Imaging Train Compatibility

The rear of the reducer features standard M48 x 0.75 threads and a 55mm backfocus requirement—matching common setups for DSLRs and cooled CMOS cameras. It also includes internal 2" filter threads, so you can drop in your favorite broadband or narrowband filters without adjusting spacing.

An M74 to M48 adapter is included to thread directly into the Esprit 120 focuser. The build quality is robust, with CNC-machined aluminum construction and fully multi-coated optics to maximize light throughput while minimizing reflections and ghosting.

Key Features:

• Designed exclusively for the Sky-Watcher Esprit 120 ED Triplet

• 0.77x reduction: 840mm becomes 646.8mm, f/7 becomes f/5.4

• 34mm corrected image circle – perfect for APS-C sensors

• Fully multi-coated optics for maximum transmission and minimal scatter

• Standard M48 rear thread with 55mm backfocus spacing

• Internal 2" filter threads (M48 x 0.75)

• Includes M74 to M48 adapter for direct attachment

• Threaded, rigid, and easy to integrate into any imaging train

Real-World Imaging Benefits

In the field, this reducer shines where it counts. It reduces exposure times while expanding the field of view—making it easier to frame large targets and complete projects faster. Star shapes remain tight across the corrected field, and the faster system improves your signal-to-noise ratio per subframe. The result is cleaner data, especially under light-polluted or variable skies.

If you’ve invested in an Esprit 120 for its optical quality, this reducer is the logical next step. It’s not just compatible—it’s designed to complete the system.