ZWO FF131 APO 131mm f/7.5 Quadruplet Refractor

ZWO's flagship 5-inch refractor for small galaxies and fine detail

The ZWO FF131 APO is ZWO's flagship 131mm (5.2") f/7.5 quadruplet apochromatic refractor, with a built-in field flattener and a full-frame 44mm image circle. Its 983mm focal length and big aperture are made for small galaxies and planetary nebulae, and it gives stunning high-power views of the Moon and planets.

Key specs: 131mm aperture · 983mm f/7.5 · 44mm full-frame image circle · built-in field flattener · 7.9kg (17.4lb) tube · 3" dual-speed rack-and-pinion focuser

What you can image and see

• Small galaxies: the Sombrero, Needle, Black Eye and NGC 891, plus galaxy groups like Stephan's Quintet.
• Planetary nebulae: the Ring, Dumbbell, Cat's Eye and Owl nebulae with real structure.
• Globular clusters: M13 and M3 resolved into thousands of stars.
• Visual: high-power views of Saturn, Jupiter and the Moon, and splitting close double stars.

No flattener, no spacing math

Most refractors need a separate field flattener set at an exact distance from the sensor. The FF131 APO's four-element, air-spaced design (with one ED element) has the flattener built in, so there's no back focus to calculate: anywhere from 42mm to 73mm of spacing behind the M48 thread, you'll reach focus with sharp stars to the corners. The included photography extension tube and M48/M54 adapters connect dedicated astronomy cameras, DSLRs and mirrorless cameras, and the 360° rotator lets you frame your target without touching focus.

What to add for the best results

• A mount (required): the ZWO AM7 is a great match. Or save time with the ZWO 131APO + AM5N bundle or the ZWO FF131 APO + AM7 bundle.
• A camera: the ZWO ASI2600MC Pro (APS-C, cooled) is a popular pairing; the ZWO ASI533MC Pro is a great-value cooled color camera with a square sensor.
• Guiding: the ZWO 30F5 Mini Guide Scope with an ASI120MM Mini guide camera mounts right on the handle.
• Control and focus: the ASIAIR PLUS runs the whole rig from your phone, and the ZWO EAFN electronic focuser keeps stars sharp as the temperature drops.
• Filters: for city and suburban skies, a ZWO Duo-Band filter in a ZWO M54 2" filter drawer cuts light pollution on nebulae.
• For visual use: a 2" star diagonal like the Celestron 2" Dielectric Star Diagonal plus your eyepieces.

FF131 APO vs. the other ZWO FF refractors

Still deciding? Browse all our refractor telescopes or the full ZWO telescope lineup.

What's in the box

• FF131 APO optical tube with handle, tube rings and dovetail plate
• Photography extension tube with M48 and M54 adapters
• User manual, inspection sheet and warranty card

Mount, camera, diagonal and eyepieces are sold separately.

ZWO FF131 APO FAQ

Do I need a field flattener with the FF131 APO?

No. The flattener is built into the optics, so stars stay sharp to the corners of a full-frame sensor, and there's no exact back focus to hit: anywhere from 42mm to 73mm of spacing behind the M48 thread, you'll reach focus.

Which camera works best with the FF131 APO?

An APS-C sensor like the ASI2600MC Pro gives about a 1.4° × 0.9° field at 983mm, great for galaxies and planetary nebulae. A smaller sensor like the ASI533MC Pro frames small galaxies even tighter. The 44mm image circle covers full-frame sensors too. DSLR and mirrorless cameras also work with the matching T-ring.

What mount do I need for the FF131 APO?

At 9.4kg (20.7lb) with rings and dovetail, the FF131 APO needs a solid mount. The ZWO AM5N handles many setups; the ZWO AM7 gives you more headroom for a heavy cooled camera, filter wheel and guide scope, and holds steadier in wind. See the ZWO 131APO + AM5N bundle or the ZWO FF131 APO + AM7 bundle for a matched setup.

Can I use the FF131 APO for visual observing?

Yes. The focuser accepts 1.25" and 2" accessories, so add a star diagonal and eyepieces. The color-free optics give crisp views of the Moon, planets and star clusters.

FF131 or FF110?

The FF131 gathers about 40% more light and reaches 983mm, so it's the better choice for small galaxies and planetary nebulae. The FF110 is lighter and easier to transport, and still covers most galaxy targets.

Specifications