Spring is galaxy season. As Leo, Virgo, and Ursa Major climb into the evening sky, the telescope begins pointing toward objects that reward a little more aperture and focal length. The Whirlpool Galaxy has spiral arms waiting to be recorded, the Sombrero Galaxy hides a dark lane of dust across its bright center, and the globular cluster M3 contains thousands of stars crowded into a relatively small patch of sky.
These are wonderful targets, but many of them appear rather small through the short focal lengths of a typical wide-field refractor. You can photograph them, certainly, but eventually you begin wishing they occupied a little more of your camera's sensor.
The ZWO FF110 APO is designed for the astrophotographer who has reached that point. Its 110mm aperture gathers approximately two and a half times as much light as a 70mm refractor, while its 766mm focal length provides more image scale for galaxies, planetary nebulae, and detailed regions within larger emission nebulae.
And it does this without adding one of the more familiar complications of refractor astrophotography. The FF110's four-element apochromatic optical design produces a natively flat field across a 44mm image circle, making it suitable for full-frame astronomical cameras without requiring a separate field flattener.
At f/7, the FF110 isn't intended to be an exceptionally fast, ultra-wide-field astrograph. Instead, it offers a thoughtful balance of aperture, focal length, optical correction, and mechanical capability. It's a telescope for someone who enjoys finding the detail within an object rather than always trying to fit the largest possible area of sky into one photograph.
More Aperture, More Image Scale
Moving from a 70mm telescope to a 110mm telescope is a more substantial step than the numbers might initially suggest. Since light-gathering area increases with the square of the aperture, the FF110 collects approximately 147% more light than a 70mm refractor, assuming comparable optical transmission.
Compared with a 90mm telescope, the FF110 provides nearly 50% more light-gathering area. It also offers greater theoretical resolving power, potentially allowing finer details to be separated when atmospheric conditions and the rest of the imaging system cooperate.
Its 766mm focal length is especially useful when photographing objects that appear relatively small in the sky. A galaxy that occupies only a modest part of the frame at 400mm or 500mm focal length becomes noticeably larger at 766mm when using the same camera.
For example, the Whirlpool Galaxy, M51, is a rewarding target for a telescope in this focal-length range. Its bright central region, spiral arms, and interacting companion galaxy form a recognizable photographic subject, with enough surrounding sky to provide context. Additional integration time can help reveal the fainter outer structures, while steady seeing and accurate guiding are important for recording finer detail.
The Sombrero Galaxy, M104, presents a different challenge. Its compact, bright central region contrasts with a narrow dark dust lane. The FF110 gives the galaxy a larger image scale than a shorter refractor would, although substantial cropping or a smaller camera sensor may still be useful when presenting a close-up photograph.
Globular clusters are another natural target. At lower resolution, an object such as M3 may resemble a compact, grainy patch of light. With sufficient aperture, appropriate image scale, and good conditions, more of its tightly packed stars can be distinguished individually.
For many imagers, this is the attraction of moving to a larger refractor: not simply recording another object, but discovering how much more detail can be found within an object they've photographed before.
Four-Element Apochromatic Optics with a Native Flat Field
The FF110 uses a fully air-spaced, four-element apochromatic optical system. Three optical elements are positioned toward the front of the telescope, while the fourth is located farther back in the tube. One of the four elements uses extra-low dispersion glass to help reduce chromatic aberration.
Chromatic aberration occurs because different colors of light refract by slightly different amounts when passing through glass. In an ordinary lens, this can cause different wavelengths to reach focus at different positions, producing colored fringes around bright stars and reducing the sharpness of the image.
An apochromatic optical design reduces those differences by combining carefully selected glass types with precisely calculated lens curvatures. The result is improved color correction, particularly important when photographing bright stars against a dark background.
ZWO does not identify the particular ED glass formulation used in the FF110. Rather than judging the telescope by the designation of one element, it makes more sense to consider the complete four-element optical design and the correction it is intended to provide.
That design also addresses field curvature, a familiar challenge in refractor astrophotography.
A conventional refractor naturally tends to form its sharpest image on a curved surface. Your astronomical camera sensor, however, is flat. When the center is sharply focused, stars near the corners may appear soft or stretched because those parts of the image fall away from the ideal focus surface.
Many refractors solve this problem with a separate field flattener installed behind the focuser. That accessory can provide excellent correction, but it normally requires the camera sensor to be positioned at a carefully specified distance behind it. Add a filter wheel, off-axis guider, or different camera, and that spacing may need to be recalculated.
The FF110 incorporates field flattening into the telescope's optical design. All four elements work together to produce a flat photographic field, eliminating the need for an additional flattener and its associated correction-spacing requirement.
That doesn't eliminate every mechanical consideration. Your camera still needs to reach focus, and the imaging train must remain properly aligned. But it removes an accessory and an adjustment that many astrophotographers would happily do without.
Full-Frame Imaging at 766mm
ZWO specifies a corrected image circle measuring 44mm in diameter, sufficient to cover the approximately 43.3mm diagonal of a standard full-frame camera sensor.
With a 36mm x 24mm full-frame camera, the FF110 produces a field approximately 2.7° wide and 1.8° high. That is considerably narrower than the field of the smaller FF70, but it still includes enough sky to photograph many medium-sized nebulae and galaxy groups without assembling a mosaic.
With a typical APS-C camera, the field is approximately 1.8° x 1.2°, depending on the sensor's dimensions. That can be an attractive framing option for smaller galaxies, globular clusters, and planetary nebulae.
Pixel size also influences the level of detail a camera can record. A sensor with 3.76-micron pixels provides approximately 1.01 arcseconds per pixel at the FF110's native 766mm focal length.
That's fine enough to make good seeing and accurate tracking increasingly important. When stars are being recorded at roughly one arcsecond per pixel, small guiding errors and atmospheric turbulence become easier to see in the finished image.
It also means the FF110 benefits from a carefully chosen mount. The additional focal length is useful, but you only receive its full benefit when the equipment can track smoothly and the telescope remains properly focused.
The 44mm image circle offers considerable camera flexibility, although full-frame imaging still demands good mechanical alignment. Camera tilt, restrictive adapters, or undersized filters can affect the outer corners of a photograph even when the telescope's optical field is properly corrected.
A 3" Focuser for a Serious Imaging System
A larger refractor is often paired with more substantial imaging equipment. A cooled camera, filter wheel, off-axis guider, and various threaded adapters can place a meaningful amount of weight behind the telescope, and the focuser must support that equipment without introducing unwanted movement or tilt.
The FF110 includes a 3" rack-and-pinion focuser with dual-speed adjustment. The large focuser provides a substantial mechanical connection for the imaging train, while its 10:1 fine-focus control allows small, precise adjustments when approaching critical focus.
That precision becomes particularly useful at 766mm focal length. Even a small focusing error can soften stars and fine detail, especially when using a camera with relatively small pixels.
The focuser also incorporates a built-in 360° camera rotator. This makes it possible to change the camera's orientation without loosening the telescope in its mounting rings or turning the entire optical tube on the mount.
For an object such as the Leo Triplet, rotating the camera can help position all three galaxies attractively within the frame. For elongated nebulae or pairs of objects, the ability to adjust the framing can make the difference between a well-balanced composition and one that feels unnecessarily cramped.
Once you've chosen the framing, secure the rotator and check focus again before beginning a long imaging sequence.
The FF110 can also accommodate a compatible ZWO EAF electronic focuser, sold separately. Electronic focusing is particularly useful for long imaging sessions because it allows compatible control software to make repeatable adjustments as temperature and observing conditions change.
Generous Rear Connections, with One Important Detail
The FF110 provides a large M78x1 rear interface and includes a 55mm extension adapter, along with threaded connections that step down to the widely used M54x0.75 and M48x0.75 camera standards.
A photographic extension assembly is also included, with an M48 thread for a standard mounted 2" astronomical filter.
This provides several ways to connect astronomical cameras and accessories, but there is an important distinction between the FF110's native flat-field design and its available back focus.
Because there is no separate field flattener, you do not have to position the camera at one exact distance to obtain the intended optical correction. You do, however, need to keep the camera sensor within the range where the focuser can bring the image to focus.
ZWO specifies an effective focusing range of 42mm to 73mm measured from the relevant M48 photographic interface. When measured from the corresponding M54 interface, the range is 60mm to 91mm. The different figures come from the different physical reference points.
Before purchasing extra adapters, add up the optical and mechanical lengths of your camera, filter wheel, off-axis guider, and any spacers. If the assembled imaging train extends beyond the available range, the camera may not reach focus even though the telescope does not require a separate flattener.
That little bit of planning is worthwhile, particularly if you're building a monochrome imaging system with several accessories behind the focuser.
Substantial Optics Without an Oversized Tube
At approximately 12.7 pounds for the optical tube and 14.9 pounds with the included mounting rings, handle, and dovetail, the FF110 is a noticeably larger instrument than the FF70 or FF90.
It's still manageable for one person, but this is a telescope that deserves a capable mount rather than the smallest tracking head you can find.
The supplied Vixen-style dovetail plate is approximately 11.8" long, providing a useful mounting and balancing surface. The detachable rings and carry handle make the tube easier to manage during setup, while finder-mounting positions allow compatible guiding or aiming accessories to be installed.
The retractable dew shield reduces the telescope's overall length during transportation. Depending on the attached rear accessories and dew shield position, the specified length ranges from approximately 26.1" to 32.1". Internal baffling and anti-reflection treatment help control unwanted stray light.
When selecting a mount, consider the total imaging weight, not simply the telescope itself. A cooled camera, filter wheel, off-axis guider, electronic focuser, and accessories all contribute additional load.
Equally important is the tube's length. A long refractor presents more leverage and wind resistance than a compact camera lens of the same weight. A stable equatorial or strain-wave mount with sufficient practical capacity will make the FF110 a much more enjoyable instrument to use.
More Than an Astrophotography Telescope
Although the FF110 is designed with serious imaging in mind, 110mm of well-corrected refractor aperture can also provide excellent opportunities for visual astronomy.
The Moon is particularly rewarding. Larger craters, mountain ranges, and the delicate shadows along the terminator become fascinating places to explore as the lunar phase changes.
Jupiter provides another opportunity to enjoy the additional aperture. Its main cloud belts, changing moon positions, and occasional atmospheric details can make for rewarding sessions. Under steady conditions, finer features may become visible, although atmospheric seeing often determines how much detail any telescope can reveal.
Saturn's rings remain a memorable sight, with the appearance of the rings and the visibility of finer divisions depending on their changing orientation and the observing conditions.
Double stars are another good match for a refractor of this size. Pairs with contrasting colors can be especially attractive, while closer pairs provide a satisfying test of optical quality, focus, and atmospheric steadiness.
On deep-sky objects, the FF110 gathers substantially more light than a 70mm instrument. Globular clusters, brighter nebulae, and open clusters benefit from that additional aperture, particularly under dark skies.
Visual observing requires a compatible star diagonal and eyepieces, which are sold separately. ZWO provides for both 1.25" and 2" visual connections, subject to the telescope's available focusing range.
Under the Night Sky
Spring is a wonderful time to put the FF110 to work. As the winter Milky Way moves westward, the evening sky opens toward the enormous collection of galaxies in Leo, Virgo, Coma Berenices, and Ursa Major.
The Whirlpool Galaxy, M51, is one of the most enjoyable photographic targets of the season. Its face-on spiral structure, interacting companion NGC 5195, and faint surrounding features reward careful imaging and plenty of integration time.
The Sombrero Galaxy, M104, lies farther south in Virgo. Its bright central region and dark equatorial dust lane produce a strikingly different appearance from M51. The FF110 provides a useful starting image scale, with additional cropping often desirable for a close-up view.
The globular cluster M3 is another excellent spring target. Its densely packed central region and many outlying stars provide an opportunity to practice focusing and exposure control while recording a remarkable collection of ancient stars.
As summer arrives, the Milky Way takes center stage. The Dumbbell Nebula, M27, in Vulpecula is a particularly rewarding subject for an instrument of this focal length. Its bright central lobes are relatively easy to capture, while the fainter outer structures benefit from additional exposure time.
The Crescent Nebula, NGC 6888, in Cygnus offers a different challenge. Its curved arcs of emission and intricate filamentary structure respond especially well to narrowband imaging. At 766mm, the FF110 provides enough image scale to make those details a central part of the composition.
In autumn, the Bubble Nebula, NGC 7635, becomes an interesting project in Cassiopeia. The glowing bubble is surrounded by a broader region of emission, and the nearby star cluster M52 can be included in a wider composition.
Winter brings the Eskimo Nebula, NGC 2392, in Gemini. It is much smaller than the summer nebulae, so recording fine structure requires excellent seeing, accurate guiding, and often a longer effective focal length. It's a good reminder that even a 766mm refractor has limits when pursuing the tiniest deep-sky objects.
For visual observers, Jupiter, Saturn, the Moon, and colorful double stars offer plenty of enjoyment between photographic projects.
Observing Tip: Give the Optics Time to Settle
A 110mm refractor contains more glass and metal than a small travel telescope, and those materials need time to approach the outdoor temperature before the instrument performs at its best.
If the telescope has been stored in a warm house and the nighttime air is much cooler, set it outside before you intend to begin serious observing or photography. Thirty to sixty minutes can be a useful starting point, although a larger temperature difference may require more time.
As the telescope cools, the optical elements and tube gradually change temperature. That can shift the best focus position, and temperature differences within the telescope may temporarily soften the image.
Once the instrument has settled, focus carefully on a suitable star. If you're imaging through the night, check focus periodically as temperatures continue to change. The exact interval depends on the conditions, the telescope, and the sensitivity of the camera.
A compatible electronic focuser makes this easier by allowing imaging software to perform repeatable focus adjustments. You can set up an autofocus routine based on time, temperature change, filter changes, or other supported conditions.
Also remember that the FF110's finer image scale places greater demands on guiding than a shorter refractor. If your stars appear elongated, examine tracking and mechanical alignment before assuming the telescope needs more optical adjustment.
The reward for a little patience is an instrument that can show you considerably more detail when the atmosphere gives it the opportunity.
FAQ
- Should I choose the FF110 or FF90 APO?
- The FF110 collects approximately 49% more light than the FF90 and provides a longer 766mm focal length compared with the FF90's 609mm. That makes it attractive for galaxies, globular clusters, and smaller nebulae. The FF90 offers a wider field, lower weight, and easier mounting requirements. Choose according to your preferred targets and the capacity of your mount.
- Does the FF110 require a field flattener?
- No. Its four-element apochromatic optical system incorporates field flattening and provides a manufacturer-specified 44mm image circle. There is no separate field-flattener correction spacing to adjust.
- Will it work with a full-frame camera?
- Yes. The 44mm image circle is designed to cover a conventional full-frame camera sensor. Proper adapter clearances and camera alignment remain important for good performance across the field.
- What is the correct back-focus distance?
- ZWO specifies a focusing range of 42–73mm from the M48 photographic interface or 60–91mm from the corresponding M54 interface. The different figures use different mechanical reference points. These are focusing limits, not a required flattener-to-sensor spacing.
- What kind of mount should I use?
- The FF110 weighs approximately 14.9 pounds with its mounting rings, handle, and dovetail, before adding camera equipment. A stable equatorial or strain-wave mount with adequate payload capacity and accurate tracking is recommended. Include the complete imaging train and consider the telescope's length when choosing a mount.
- Is the FF110 suitable for planetary observing?
- Yes. A 110mm apochromatic refractor can provide rewarding views of Jupiter, Saturn, Mars, and the Moon. The detail visible depends on magnification, atmospheric seeing, planetary position, and observing conditions. High-resolution planetary photography may benefit from additional effective focal length and a suitable planetary camera.
- Can I install a ZWO EAF electronic focuser?
- Yes. The FF110 provides mounting provisions for a compatible ZWO Electronic Automatic Focuser. The focuser and any necessary mounting components are sold separately.
- Can the FF110 be used visually?
- Yes. The telescope supports appropriate 1.25" and 2" visual connections. A compatible star diagonal and eyepieces allow it to be used for planetary, lunar, double-star, and deep-sky observing.
What's Included
- ZWO FF110 APO 110mm f/7 flat-field apochromatic refractor optical tube
- Detachable mounting rings with carry handle
- 11.8" Vixen-style dovetail mounting plate
- Photography extension assembly with 2" filter thread
- M78x1 55mm extension adapter
- M78x1 to M54x0.75 threaded adapter
- M54x0.75 to M54x0.75 threaded adapter
- M54x0.75 to M48x0.75 threaded adapter
- 1.25" and 2" visual connection adapters
- User manual
- Inspection certificate
- Warranty card
Mount, camera, electronic focuser, guiding equipment, filters, star diagonal, and eyepieces are sold separately.
Optional Accessories
ZWO Electronic Automatic Focuser (EAF): Provides motorized focusing and can help maintain accurate focus during changing nighttime temperatures when used with compatible control equipment.
ZWO Off-Axis Guider and Guide Camera: Allows guiding through the main telescope's optical path, helping reduce differential flexure when photographing at 766mm focal length.
Electronic Filter Wheel or Filter Drawer: Provides a convenient way to change imaging filters when photographing broadband and narrowband targets.
Mounted 2" Astronomical Filters: Compatible filters can be installed using the photographic extension assembly's M48 filter thread. If using an off-axis guider, consider locating restrictive filters behind the guider's prism to avoid unnecessarily dimming guide stars.
Star Diagonal and Eyepieces: Turn the FF110 into a capable visual instrument for observing planets, the Moon, double stars, and brighter deep-sky objects.
Final Thoughts
There's something particularly satisfying about returning to a familiar object with a little more aperture and focal length. A galaxy that once appeared as a small smudge begins to show structure. A globular cluster that looked grainy starts to resolve into individual stars. A planetary nebula that seemed featureless may reveal hints of its more complicated shape.
The ZWO FF110 APO is built for that kind of progression.
Its 110mm aperture and 766mm focal length provide a meaningful step beyond the smaller FF-series refractors, while the four-element, natively flat optical system makes it possible to use a full-frame camera without adding a separate field flattener.
The substantial 3" focuser, camera rotator, and included threaded adapters also make sense for someone assembling a more complete astrophotography system. With a capable mount, accurate guiding, and careful focus, the FF110 is well suited to a broad range of photographic projects.
It does ask a little more of its owner. The tube is heavier, the focal length places greater demands on tracking, and the additional glass benefits from time to adjust to the nighttime temperature. These aren't unusual requirements for a refractor of this size, but they're worth understanding before choosing one.
For someone primarily interested in enormous nebulae and the widest possible fields, a smaller refractor may still be the better choice. But for the photographer who enjoys galaxies, planetary nebulae, globular clusters, and the finer structures within larger deep-sky objects, the FF110 offers a very appealing combination of capability and convenience.
And when spring brings the galaxies back into the evening sky, you'll have an instrument ready to spend a few long, enjoyable nights exploring them.
