ZWO FF110-APO 110mm Quadruplet Refractor F/7.0

A 110mm f/7 Imaging and Visual Platform

The FF110-APO is engineered as a versatile instrument for both high-resolution astrophotography and immersive visual observation. The 110mm (4.33") aperture strikes a balance between light-gathering capability and physical size, while keeping the tube a manageable size. At a focal ratio of f/7, the telescope is well-suited for a wide range of celestial targets.

For imagers, the 766mm focal length suits many popular nebulae and larger galaxies on full-frame and APS-C sensors. For visual observers, this focal length produces moderate magnifications suited to globular clusters, observing planetary detail, and sweeping through rich star fields with a low-power, wide-field eyepiece.

4-Element APO Optics with ED Glass

At the heart of the FF110-APO is a four-element, air-spaced apochromatic optical design. Three elements sit at the front and one at the rear, and together they deliver a flat field without a separate corrective lens. One Extra-Low Dispersion (ED) glass element effectively reduces chromatic aberration, or false color.

The ED element helps bring different wavelengths to a common focus, reducing the purple or blue halos that chromatic aberration produces around bright stars.

A 44mm Image Circle with Native Field Correction

A key feature of the ZWO FF110-APO is its native flat-field design, which produces a 44mm image circle. This field covers full-frame (36x24mm) sensors without a separate field flattener, and it delivers sharp star fields with excellent edge-to-edge performance.

This integrated correction greatly simplifies the imaging setup. You no longer need to spend time calculating and adjusting the critical back focus distance required by external flatteners. Focus can be achieved when the total rear connection length is between 42 mm and 73 mm. This allows you to connect your camera and begin imaging immediately, saving valuable time under clear skies.

3-Inch Rack-and-Pinion Focuser with 1:10 Fine Adjustment

The FF110-APO is equipped with a rigid 3-inch dual-speed rack-and-pinion focuser with 31mm of travel.

Achieving critical focus is made simple with the dual-speed 1:10 fine adjustment knob, allowing for precise, minute movements of the focuser. For framing, the focuser also includes a 360° rotator at the rear for precise angle adjustment. The focuser has screw positions for an EAF bracket, so ZWO's EAF (Electronic Automatic Focuser, sold separately) can be fitted for motorized focusing.

Flexible 42-73mm Back Focus and Camera Connections

The FF110-APO offers significant flexibility in connecting your imaging gear. Instead of a single, fixed back focus distance, it provides an effective focus range of 42mm to 73mm, measured from the M54-M48 imaging interface. This means any camera and accessory combination with a total optical path length within this range can achieve focus.

To facilitate these connections, the telescope includes a photography extension tube that provides two standard male thread sizes for direct attachment of your camera and accessories.

• M54x0.75 Male Thread: For connecting to larger filter wheels or accessories that use this thread standard.
• M48x0.75 Male Thread: A common thread for astronomy cameras and T-rings; this adapter also has a built-in 2-inch filter thread.

CNC-Machined Build with Imaging-Focused Details

The entire lens tube of the FF110-APO is CNC machined with a high-quality paint finish, and an internal baffle and anti-reflection coating suppress stray light and improve contrast. A retractable dew shield, with an outer diameter of 143mm, helps prevent moisture from forming on the objective lens and blocks off-axis light.

Several features are included to streamline the setup process for astrophotography.

• Mounting Hardware: The telescope comes with a set of mounting rings, a carrying handle, and a 300mm Vixen-style dovetail plate.
• Finder Bases: The handle has a finder base slot and two more finder bases sit on either side of the focuser, so a finder scope can be moved without disassembly and other accessories can be mounted.
• Quick-Release Rings: The rings use a clamshell design with large thumb screws, enabling quick, tool-free installation and removal of the optical tube.

14.9 lb Weight, 664mm Length, and Mount Requirements

The ZWO FF110-APO has a fully assembled weight of 14.9 lb, which includes the optical tube, rings, handle, and dovetail. The bare optical tube itself weighs 12.65 lb. With the dew shield retracted, the tube has a compact length of 664mm, making it relatively easy to transport and store. This combination of aperture and weight places it in a class that requires a stable, mid-sized equatorial mount.

When choosing a mount, add the weight of your camera, guide scope and other accessories to the telescope's 14.9 lb and compare the total with the mount's rated payload, leaving headroom for stable long-exposure tracking.

ZWO FF110-APO vs. FF90-APO: Image Scale and Portability

The primary decision between the ZWO FF110-APO and its 90mm sibling comes down to a choice between image scale and portability. Both feature the same quadruplet flat-field optical design, but their different apertures and focal lengths make them suited for different applications and mounts.

• ZWO FF90-APO Advantage: At a lower weight, the FF90-APO is compatible with lighter and more portable equatorial mounts. Its wider field of view from the shorter 609mm focal length is also better suited for capturing extremely large targets like the North American Nebula (NGC 7000) in a single frame.
• ZWO FF110-APO Advantage: The 766mm focal length of the FF110-APO delivers greater magnification and a tighter image scale. This allows you to resolve more intricate details on smaller galaxies, planetary nebulae, and galaxy clusters with the same camera sensor, filling the frame with your target. The larger 110mm aperture also provides greater light-gathering power and higher theoretical resolution.