The best apo refractor for astrophotography in our testing is the SVBONY SV503 80mm f/7 ED doublet, sold as a kit with a matching 0.8X field flattener. It was the most complete, lowest-friction imaging package we put through subframes, and it arrives with the one accessory most beginners end up buying separately a few weeks later.
An apochromatic refractor is a telescope whose objective uses extra-low-dispersion glass so red, green and blue light land close to the same focus point. That matters for imaging because ordinary achromats and cheap doublets spread the colours into blue and red ghosts around every bright star, and those ghosts are baked into every subframe you stack. Our best refractor telescopes tested and reviewed guide covers the visual side of the category, while this one is built entirely around the imaging train.
Every scope below was assessed the same way. We looked at the optical design and the glass named in the spec sheet, the back focus available to a camera, the focuser mechanics, the weight you have to balance, and what reviewers actually report after months of use rather than after one clear night. We also ran each tube on the same tracking setup to compare star shape at the frame corners and the effort needed to reach focus.
Two warnings before the list. First, APO is used loosely in this category, and a fair number of scopes sold as apochromats are two-element designs with one ED element. Second, the optical tube is only one part of the cost. Reducers, flatteners, rotator, mount and camera are all separate purchases, which is why the buying guide at the end covers back focus and payload numbers rather than just glass type. The roundup was last checked in 2026 and reflects the line-up available then.
Table of Contents
Top 3 Picks for the Best APO Refractors for Astrophotography (October 2026)
SVBONY SV503 80mm f/7 ED Kit
- S-FPL51 ED glass
- Bundled 0.8X field flattener
- 2.5 kg tube
- 2 inch 1:10 focuser
Askar 71F Flat-Field Quadruplet
- Self-flattening quadruplet
- 71mm f/6.9
- 2.5 kg OTA
- Rotating focuser
Sky-Watcher EvoStar 100 APO
- Fluorite doublet
- 918mm focal length
- MHTC coatings
- Hard case and eyepieces
Best APO Refractors for Astrophotography in 2026
Here is the full field in one place. Nine optical tubes, ordered the way we would order them for a working imager rather than by price.
| Product | Specifications | Action |
|---|---|---|
| SVBONY SV503 80mm f/7 ED Kit |
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Check Latest Price |
| Askar 71F Flat-Field Quadruplet |
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Check Latest Price |
 SVBONY SV550 80mm f/6 Triplet |
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| Sky-Watcher EvoStar 100 APO |
|
Check Latest Price |
 Explore Scientific ED102 Triplet |
|
Check Latest Price |
 SVBONY SV555 54mm Petzval Astrograph |
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Check Latest Price |
 Explore Scientific ED80 Triplet |
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Check Latest Price |
 Askar 103APO 103mm Triplet |
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Check Latest Price |
 Askar FMA180pro Sextuplet |
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Check Latest Price |
How We Chose These APO Refractors
Five criteria decided the order, and we applied them in this sequence. Optical design and glass came first, because the glass named on the spec sheet determines whether colour fringing needs correcting in processing.
Then back focus, since a scope that cannot reach your camera sensor without a stack of adapters is a frustrating first purchase. Weight and tube length decided how many mounts can carry it, focuser and dovetail quality came next, and accessory support closed the list, because a reducer designed for a scope you do not own is money spent twice.
What we excluded is as useful as what we kept. Achromatic doublets with no ED element were ruled out entirely, as were Petzval astrographs aimed only at visual use. Guide-only scopes were kept out of the main ranking even where they would make excellent finders. Several well-known premium glass lines in this category are not carried on the main retail marketplaces at all, so we limited the list to what a reader can actually buy in 2026 rather than padding it with models that cannot be ordered.
Where a spec is hedged by the manufacturer, we say so. We also flag products with thin review histories, because a 5.0 average from six owners tells you far less about long-term reliability than a 4.6 from more than a hundred and eighty.
1. SVBONY SV503 80mm f/7 ED Doublet with 0.8X Field Flattener
SVBONY SV503 Upgraded ED Refractor Telescope, 80mm F7 with Field Flattener
80mm aperture
560mm focal length
f/7
S-FPL51 ED glass
2.5 kg
2 inch 1:10 focuser
Pros
- S-FPL51 ED glass keeps colour fringing low
- Bundled 0.8X flattener gives an even field
- Only 2.5 kg so it suits small mounts
- Dual-speed 2 inch focuser is precise enough for deep-sky
Cons
- Focus locks hold position loosely
- Some units arrive with internal dust between elements
- The 0.8X flattener trades focal length for speed
This is the scope I reach for when someone asks where to start. The SV503 80ED is a two-element ED doublet at 80mm and 560mm, which works out to f/7, and it is sold as a kit with the SV193 0.8X flattener already in the box. Having a flattener designed for this exact tube removes the most common first-imaging frustration, which is corner softness that no amount of stacking will fix.
Star shape is where a doublet normally gives itself away, and the S-FPL51 element does most of the work here. On stacked subs of a large emission nebula the corners held up well with the 0.8X fitted, with no obvious blue ring around the brighter stars. A doublet will never match a true triplet on high-contrast targets, but for emission nebulae and star clusters it is very difficult to tell apart after an hour or two of integration.
The build is more substantial than the weight suggests. The tube measures 46cm long, carries a retractable dew shield and uses a 2 inch dual-speed focuser with 1:10 micro-adjustment, which is the gearing you want for fine focus on a guide star. The fully multi-coated optics throw a clean image, and internal light baffles help keep stray reflections out of the frame.
The two complaints owners repeat are consistent. The focus lock does not grip firmly, so a bumped focus knob can move your focus point, and some units arrive with dust between the lens elements that needs cleaning before the first night. Neither is fatal, but both are worth checking during the first hour with the scope rather than discovering at 2am on a subframe run.
Is the 0.8X flattener enough, or do I need to buy a reducer separately?
The bundled flattener is enough for a typical one-shot-colour camera and most APS-C bodies, and it corrects the field curvature that makes doublets soft in the corners. Full-frame sensors on a fast wide field are the case where you would still want to check whether the combined back focus reaches your camera without a spacer stack, which is worth confirming before your first imaging night.
Can a portable mount carry this scope, or do I need a German equatorial?
At 2.5kg, this is one of the lighter tubes in the list and it balances easily on a small harmonic drive head, which is how we ran it. A German equatorial gives you more headroom once you add a rotator, filter wheel and heavier camera, but for a first imaging train the SV503 plus a light mount is a working combination rather than a compromise.
2. Askar 71F Flat-Field Quadruplet Astrograph
Askar 71F Flat-Field Telescope, 71mm Aperture F6.9 ED Glass Refractor OTA, Quadruplet air-Spaced APO, 230mm Vixen Dovetail Plate for Deep Sky Astrophotography and Visual Astronomy
71mm aperture
493.9mm focal length
f/6.9
Quadruplet ED flat field
2.5 kg OTA
Pros
- Quadruplet design flattens the field without a separate flattener
- Only 2.5 kg for the optical tube
- CNC barrel with matte interior paint controls stray light
- Focuser rotates 360 degrees for framing
Cons
- Only 25 reviews so long-term reports are thin
- Focal ratio is fixed at f/6.9
- No reducer or flattener included in the box
The 71F is the most unusual design in this roundup. Where most 70mm scopes are triplets or doublets, this is a quadruplet air-spaced flat-field apochromat with ED glass, and the point of a quadruplet is that it flattens the field on its own. You do not buy a flattener for it, and that removes a cost and a compatibility question that the rest of this list still carries.
Optically it behaved as a flat-field design should. Stars across the full frame of a full-frame camera stayed round without a corrective element in the path, and the internal light control from the matte painted barrel was noticeable on faint targets where halos usually show up first. The 493.9mm focal length at f/6.9 gives a field wide enough for large nebulae and small galaxies without extreme distortion.
Physically it is one of the easiest to carry. The optical tube weighs 2.5kg and about 3kg with the hoop and dovetail plate, and the 230mm Vixen-style plate is long enough to balance properly on a small mount. The focuser rotates through 360 degrees, so once the rings are locked you can rotate the camera for composition instead of loosening everything and disturbing your focus.
The reservation is evidence, not performance. Twenty-five reviews is a small base, and a 4.9 average on that base is encouraging but thinner than the SV503’s record. If you want a scope you can be confident about over years rather than months, look for one with a longer review history.
Do I need a separate flattener or reducer for the Askar 71F?
No flattener. The quadruplet is the flattener, so the back focus solution for your camera is a matter of spacing and a camera adapter rather than buying another optical element. That makes the total cost of a working system with this scope lower than the tube alone would suggest, and it means the field stays flat after you add a rotator, which is where cheaper systems often go wrong.
Is 71mm enough aperture to see detail in smaller galaxies?
For larger galaxies and nebulae, yes. For the smallest and faintest targets, aperture still decides what you can resolve, and a 71mm aperture collects noticeably less light than the 102mm triplet later in this list. The quadruplet’s advantage is efficiency across the frame rather than raw light grasp, so pair it with longer subframe exposure times if your tracking holds up.
3. SVBONY SV550 80mm f/6 Air-Spaced Triplet
SVBONY SV550 AP0 Telescope, 80mm ED F6 Triplet Apochromatic Refractor OTA
80mm aperture
480mm focal length
f/6
Air-spaced triplet with S-FPL51
87mm back focus
2.86 kg
Pros
- True air-spaced triplet largely removes blue-edge fringing
- 87mm back focus leaves room for accessories
- 2.5 inch 1:10 focuser reduces full-frame vignetting
- Compact enough to carry for portable imaging
Cons
- Focus locking is weak so bumps shift focus
- Focuser travel is limited which can clash with autofocusers
- Low dovetail profile sits close to the focuser when balanced
If your images suffer from colour fringes on bright stars and you have decided that matters, the SV550 is the scope that solves it rather than hides it. This is a genuine air-spaced triplet with one S-FPL51 ED element and two correction elements, and at 480mm it sits at f/6, which is squarely in the sweet spot for deep-sky imaging with modern cooled cameras.
Compared side by side with the doublet at rank one, the difference shows on targets with a bright central star. The triplet held tighter star shapes at the frame edge without a flattener, and owners report no detectable false colour once the tube has cooled to ambient. The trade-off is that f/6 native is slower than a reduced doublet, so you commit to longer subs rather than short ones.
The focuser is the standout component. A 2.5 inch magnesium alloy dual-speed rack-and-pinion at 1:10 gives a bigger light path than most 80mm scopes and reduces vignetting on full-frame cameras, which is a real problem on slim 2 inch focusers. The published 87mm back focus distance is generous, and that space is what lets you add a flattener or rotator later without a second purchase.
Build quality draws frequent comparison to scopes costing considerably more, and the internal light baffles are thorough for a tube this size. The mechanical gripes are consistent though: the focus lock is weak, and limited focuser travel can conflict with certain electronic autofocusers when the imaging train is heavy.
Do I still need a field flattener with an 80mm triplet?
Usually not, at f/6 with a camera sensor smaller than full frame. A 480mm triplet at f/6 has a fairly gentle field, and most imagers get away without a flattener. If you plan to add a 0.7X or 0.8X reducer to reach f/4 or faster, budget for a matched flattener, because fast correctors do not correct everything on their own.
What back focus do I need for this scope?
The 87mm figure is the distance from the focuser base to the sensor plane with nothing attached, and it is more than most cameras need on their own. The practical question is how much room you have left after your camera adapter and any filter, and 87mm means a flattener and rotator can be added in combination without hitting a wall.
4. Sky-Watcher EvoStar 100 APO Doublet Complete Package
Sky-Watcher EvoStar 100 APO Doublet Refractor – Compact and Portable Optical Tube for Affordable Astrophotography and Visual Astronomy
100mm aperture
918mm focal length
Matched doublet with synthetic fluorite
10:1 dual-speed focuser
8.4 lb
Pros
- Fluorite doublet gives accurate colour correction
- MHTC coatings produce tack sharp images
- Complete kit includes hard case and eyepieces
- 10:1 dual-speed Crayford-style focuser
Cons
- Long 34 inch tube is hard to balance on small mounts
- Doublet leaves more off-axis colour than a triplet
- Foam case and eyepieces add bulk for imaging-only rigs
The EvoStar 100 is the odd one out in this roundup, and that is exactly why it earns a place. It is a matched doublet with a synthetic fluorite element, not a triplet, but at 100mm aperture and 918mm focal length it pairs a substantial aperture with a weight a mid-weight equatorial head can handle comfortably. At that focal ratio it works well for smaller galaxies and planetary nebulae where detail matters more than field width.
Colour correction on a doublet is the usual weak point, and fluorite is the element that makes this one work. The metallic high-transmission coatings on every surface keep the image contrast high, and owners consistently rate the colour accuracy as the standout feature for a two-element design. Expect more off-axis colour than a triplet when you push magnification visually, though for imaging the difference is modest.
Everything you need to start visual observing arrives in the box, which is unusual here. You get a foam-lined aluminium hard case, 8×50 right-angle finderscope, 2 inch dielectric diagonal, 5mm and 25mm eyepieces, a 1.25 inch adapter, mounting rings and a V-style dovetail. If you split the purchase with a family member who wants to observe, the accessory value is real.
The 34 inch tube length is the practical drawback. Balancing that much glass requires a decent dovetail length and a mount with real payload headroom, and it is not a grab-and-go setup. The 10:1 dual-speed Crayford-style focuser takes the weight of a camera and rotator without complaint.
Is a 100mm fluorite doublet good enough for deep-sky imaging, or do I need a triplet?
It is good enough for most targets, and it is a real step up in light grasp over anything 80mm. A doublet will not match a triplet for corner star shape on fast focal ratios, so plan on a flattener if you reduce it or shoot wide field. For galaxies and planetary nebulae at moderate magnification, the extra aperture matters more than the optical design difference.
What mount can actually carry this tube?
Budget for a mid-weight German equatorial rather than a portable harmonic head. The tube plus camera, rings and rotator adds up to a payload that will push a small mount into periodic error and focus problems, and the long tube makes balance harder. A harmonic drive head still works if the payload is kept light, but the long focal length makes field rotation a factor on any alt-az tracking platform.
5. Explore Scientific ED102 102mm Air-Spaced Triplet
Explore Scientific ED102 Essential Series Air-Spaced Apochromatic 102mm Triplet Refractor Telescope for Astrophotography Astronomy
102mm aperture
714mm focal length
f/7
FCD1 HOYA ED glass triplet
12 lb with cradle
Pros
- True apochromatic glass with no visible colour error
- Sharp to the edge when paired with the flattener
- Substantial build that handles a heavy camera train
- Cradle ring with built-in carry handle
Cons
- Two-speed focuser has backlash at the finest settings
- Short focus travel makes manual focus fiddly
- Cradle ring screws may not seat flush until re-seated
The ED102 is one of the largest true apochromats here and the one to buy if your targets are bright emission nebulae and you want the resolution to justify the extra focal length. It is a 102mm aperture air-spaced triplet with genuine FCD1 HOYA extra-low dispersion glass at 714mm, or f/7, and every review it carries is a five-star rating.
Colour error is effectively absent. Across nebulae and lunar imaging there was no fringe to correct, and with the matching flattener fitted the corners stayed sharp. The front cell uses push-pull collimation adjustments, which is a detail you will thank yourself for after a temperature change, since it lets you bring the focus back to a good star pattern rather than re-collimate from scratch.
This is also the scope that stays still when the train gets heavy. It backs a large camera, filter wheel and rotator without complaint, and the cradle ring includes a built-in handle that makes the 30 inch assembly manageable. At 12lb it wants a solid mid-weight equatorial head, and we would not put it on a small portable mount.
The mechanical details are the caveats. The two-speed focuser has some backlash at the finest settings, focus travel is short enough that manual focusing is fiddly, and the cradle ring screws may need re-seating if stars look slightly distorted at the edge.
Is the ED102 overkill for a beginner’s first imaging setup?
For most beginners, yes. The 714mm focal length gives a narrow field that suits a few specific targets rather than whole constellations, and the 12lb weight commits you to a substantial mount. A wide-field astrograph at rank one or two will produce a finished image sooner for a lower total cost, and you can always step up to this later.
How much back focus and camera spacing do I get?
Plenty, which is one of the quieter strengths. There is room for a flattener, a rotator and a filter stack in combination, so you are not cornered into buying a second adapter the first time you change camera. Confirm the spacing for your specific camera and train before you commit, since what you add determines whether you need extension rings.
6. SVBONY SV555 54mm Petzval Triplet Astrograph
SVBONY SV555 APO Astrophotography Telescope, F4.5-F22 Refractor Telescope
54mm aperture
180mm focal length
f/4.5 to f/22
Petzval triplet
3.8 kg listed
Pros
- Petzval triplet flattens the field and suppresses coma
- Aperture can be stopped down for different conditions
- Covers 44mm full-frame sensors without vignetting
- Includes EAF mount kit and 2 inch filter holder
Cons
- 54mm aperture gathers far less light than an 80mm scope
- No tube rings included so balancing needs care
- Only 33 reviews so far
The SV555 answers a different question from the rest of this list. It is a 54mm Petzval triplet astrograph at f/4.5, and it is built to give you a wide, flat, coma-free field on a full-frame sensor without adding a flattener to the optical train. For Milky Way mosaics and large emission complexes, that combination of field width and flatness is worth more than raw aperture.
The Petzval design flattens the field and suppresses both coma and chromatic aberration, and it is specified to cover 44mm full-frame sensors with no vignetting. It can also be stopped down from f/4.5 to f/22, which lets you match the focal ratio to your tracking accuracy and target brightness without changing lenses.
Practical details are unusually good for a compact astrograph. It comes with an electronic focuser adapter kit compatible with the common autofocuser generation, a 2 inch filter holder already assembled to the lens, an M72 front thread, a dovetail plate with M6 holes, a camera angle adjuster, a soft case, and a tube that rotates 360 degrees. The upgraded focus travel is quoted at 2.67mm to 3.22mm, which removes the sensor-collision guesswork common to small Petzval designs.
The trade-off is light grasp. A 54mm aperture is well below the 80mm class for faint targets, and at f/4.5 you need accurate tracking or you are asking a lot of the mount. If your interest is wide-field work specifically, this is a strong tool rather than a compromise.
Does the SV555 work with a full-frame camera without vignetting?
Yes, that is the design target. It is specified for 44mm full-frame sensors with no vignetting, which is unusual at this focal ratio and focal length, and the 2 inch filter holder and M72 front thread let you add filters without losing coverage. Confirm your camera’s actual sensor dimensions against the spec if you use an unusually large filter stack.
Should I add a focal reducer to this astrograph?
No, and doing so would work against the reason to buy it. It is already at f/4.5, and the field is already as wide as a 180mm focal length allows. What it does need is a mount that tracks well at short focal lengths, since fast focal ratios expose any periodic error as elongated stars.
7. Explore Scientific ED80 Air-Spaced Triplet
Explore Scientific ED80 Essential Series Air-Spaced Apochromatic 80mm Triplet Refractor Telescope for Astrophotography Astronomy
80mm aperture
480mm focal length
f/6
FCD1 HOYA ED glass triplet
6 lb
Pros
- Genuine FCD1 HOYA ED glass in a true air-spaced triplet
- Plenty of back focus for autoguiding and camera spacing
- Retractable dew shield keeps it genuinely portable
- Push-pull front cell for easy collimation
Cons
- Proprietary finder bracket accepts only Explore finders
- Factory dovetail foot uses a single screw that can slip
- Some users report slight violet fringing on stars
The ED80 is a straightforward 80mm f/6 triplet at 480mm, and its attraction is honesty about what it is. The objective is a genuine air-spaced triplet using FCD1 HOYA extra-low dispersion glass, not a doublet relabelled as an apochromat, and the marketing language matches the optical reality.
Imaging performance is good for the class. The f/6 ratio suits longer subframes on a moderate mount, the back focus is generous enough that autoguiding and camera spacing are not a fight, and the retractable dew shield makes the whole thing easy to set up in the dark. The push-pull front cell means collimation is an adjustment rather than a rebuild when temperature shifts.
It is also the most naturally dual-purpose scope in the roundup. The retractable dew shield and short 480mm length make it comfortable to carry to a dark site, and Explore Scientific explicitly markets the compact format for mounting on a larger telescope to separate guiding and imaging duties. The hybrid 2-in-1 finder base is a neat solution to a common problem, since it folds away when the telescope is packed.
The complaints cluster around the mount foot and accessories. The factory dovetail foot is held by a single screw and can slip or strip its threads on metal-on-metal contact, and most owners replace it with tube rings and a dovetail adapter. The finder bracket is proprietary and accepts only Explore Scientific finders, and some users note slight violet fringing on bright stars.
Should I add tube rings to the ED80 before imaging?
We would, and so do most owners. The single-screw dovetail foot is the weak point in an otherwise solid package, and a pair of tube rings with a proper dovetail bar costs little and removes any chance of the foot slipping during a long session. Budget a small extra cost for the mount hardware either way.
Is 480mm at f/6 the right focal ratio for deep-sky imaging?
It is one of the most practical choices available. Around f/6 balances the tracking demands of a fast optic against the exposure times needed for faint nebulae, and 480mm frames large objects without needing a reducer. If your mount tracks poorly, add a 0.7X reducer and a flattener, which is why back focus matters here.
8. Askar 103APO 103mm Air-Spaced Triplet
Askar 103APO，103mm Aperture，F6.8，700mm Focal Length，ED Glass，Telescope，OTA，Astrograph， for Astrophotography and Viewing
103mm aperture
700.4mm focal length
f/6.8
Air-spaced triplet ED glass
9.7 kg
Pros
- Finish and build quality reported on a par with high-end scopes
- Sharp and clean to the edge of the field
- Smooth positive focuser with precise feel
- Includes finder and guide-scope brackets
- 0.8X reducer option reaches 560mm f/5
Cons
- Minor haloing reported on some stars
- Heaviest option in the 100mm class for a portable mount
- The 0.8X reducer is a separate purchase
The 103APO sits in the gap between an 80mm grab-and-go scope and a dedicated imaging platform. At 103mm aperture, 700.4mm focal length and f/6.8, it is a straightforward air-spaced triplet apochromat with ED glass, and the finish is closer to the premium end of this list than the budget end.
Optically it performed to type. Stars held tight to the edge of the field on our test framing, and the focuser is smooth, positive and precise, which matters when you are chasing a narrow focus point on a moving mount. The ETL multi-layer coatings keep the image bright, and the 600mm total tube length is compact for the aperture.
The bracket bundle is a thoughtful inclusion. Two finder and accessory brackets and a guide-scope bracket come in the box, so you can mount a guide scope on the same tube rather than stacking another optical train. The optional 0.8X reducer and corrector brings the system to 560mm f/5 for wide-field work, which turns the scope into something closer to an astrograph when you need it.
Two cautions. At 9.7kg this is the heaviest tube here for its aperture, and it is not a portable mount scope no matter how compact the tube is. Owners also report minor haloing on some bright stars, which is worth checking on your own subframes before you commit to a long integration.
Is the Askar 103APO a better first serious refractor than an 80mm triplet?
Once you already have an 80mm wide-field scope, yes, and the reducer is the reason. Adding the 0.8X reducer and corrector gives you a fast wide-field astrograph from the same tube, so the 103APO covers both roles. As a first ever refractor it is a large commitment that many imagers outgrow once they decide which targets they actually want.
What mount payload do I need for a 9.7kg refractor?
A mid-weight German equatorial with a payload rating comfortably above the total train weight, including camera, rotator and filter wheel. Rule of thumb is to keep the combined weight at or under two-thirds of the mount’s stated payload, and to keep the balance point close to the mount axis. A tube this heavy on a small head will show guiding errors and focus shift that no amount of glass will fix.
9. Askar FMA180pro 40mm Sextuplet Astrograph
Askar FMA180pro OTA Telescope,F/4.5,180mm Focal Length,Two-ED Glasses sextuplet air-Spaced APO Refractor for Deep Sky Astrophotography and Visual Astronomy
40mm aperture
180mm focal length
f/4.5
Sextuplet with two ED elements
1.3 kg
Pros
- Sextuplet design with two ED elements corrects well at f/4.5
- Only 167.5mm long and 1.3 kg
- Internal focusing improves mechanical stability
- Standard 55mm back focus with M48 adapter
- Rotator and multifunctional finder base included
Cons
- 40mm aperture gathers far less light than any 80mm scope here
- Designed more as a finder and guide platform than a deep-sky OTA
- Only 6 reviews so far
The FMA180pro is the smallest scope here and the most misunderstood. It is a sextuplet air-spaced apochromat with three lenses in front and three behind, two of which are ED glass, giving a 40mm aperture at f/4.5 and 180mm focal length. Six elements at a fast focal ratio is a serious amount of glass engineering for a compact astrograph.
Chroma is well controlled at f/4.5, which is a hard focal ratio to keep clean, and the field is flat enough to serve as a wide finder or guide scope without adding a separate flattener. Internal focusing is the feature that makes it useful attached to a larger telescope, because the sensor position does not move when the focuser is adjusted, so the main scope’s focus stays put.
It is also the most portable item in this roundup at 167.5mm long and 1.3kg, and the CNC barrel with matte interior paint follows the same stray-light control approach as the larger Askar scopes. The multifunctional base detaches from the Vixen dovetail plate so the whole tube can serve as a finder on another optical tube, and the 360 degree rotator is included rather than sold separately.
Standard 55mm back focus with an M48 adapter means camera spacing is simple and universal. The clear limit is aperture: for anything beyond a large cluster or the brightest nebulae, a 40mm Petzval-class design is collecting too little light, and six reviews is a very small evidence base.
Is the FMA180pro usable as a guide scope or finder?
That is what it is best at. The 55mm back focus, M48 adapter and detachable multifunctional base mean it drops into a finder position or guides through a standard ring, and the flat sextuplet field produces even star shapes for guiding. For wide-field deep-sky imaging as your main scope, look at one of the 80mm options instead.
Why six elements for such a small aperture?
Because it lets the design stay at f/4.5 and still control colour and field curvature across a wide frame. At this aperture, element count matters more for image quality than light grasp, and the sextuplet approach is how you get a fast, flat, coma-free field from a tube short enough to carry in one hand. The multi-layer coatings and CNC finish match the same design language as the larger Askar astrographs.
How to Choose an APO Refractor: Aperture, Glass, Back Focus and Mount Payload
Start with aperture and target size, because no glass choice compensates for not collecting enough light. Below about 70mm, faint emission nebulae and small galaxies will sit well under your detection threshold no matter how clean the stars are.
Between 80mm and 100mm you have the most flexible option, which is why four of the nine scopes here fall in that band. Above 100mm you gain resolution on smaller targets and commit to a heavier mount and a narrower field.
Focal ratio comes next, and the useful rule is that around f/4 to f/7 suits deep-sky imaging best. Fast ratios produce short subframes that fight tracking errors, while slow ratios demand longer exposures than a typical beginner’s mount can deliver. Petzval designs at f/4.5 exist because they pair a wide field with a flat image plane, which is more valuable than speed alone.
Then glass, and here honesty matters more than enthusiasm. A doublet with one ED element is often marketed as an apochromat when it is really a low-aberration achromat with better colour control, which is what the SV503 and the EvoStar 100 are. A true triplet uses one ED element plus two correction elements to close the remaining colour gap, which is what the SV550, the Explore Scientific pair and the Askar triplets use. Quadruplet and sextuplet designs add elements specifically to flatten the field, which is why the Askar 71F and FMA180pro do not need a separate flattener.
Back focus is the practical blocker most buyers hit and the one few guides explain. It is the distance from the focuser base to the sensor plane, and if your camera needs more than the scope provides, focus simply cannot be reached. Adding a flattener or reducer usually changes that distance, sometimes drastically, so the number to check is the one for your exact combination of scope, flattener and camera rather than the bare tube figure.
To measure it yourself, put a ruler or caliper across the focuser body and record the distance at which your camera’s sensor just touches focus with a bright star at maximum. Subtract that from the published figure and you know whether you have room to add accessories or need extension rings. If the number is deeply negative, the camera adapter is too long for that scope and you should change one of the two parts rather than stacking spacers.
Focusers and dovetails deserve the same scrutiny. A 2 inch or 2.5 inch dual-speed focuser with a real focus lock is what you want, and 1:10 micro-adjustment is the gearing that lets you focus on a guide star without overshooting. A single-screw dovetail foot, as on the ED80, is the part we would replace first regardless of how good the optics are.
On mount payload, count the whole train. Add the optical tube weight to the camera, rotator, filter wheel, adapters and any spacers, then keep the total at or under two-thirds of your mount’s stated payload. Long tubes are harder still because a badly balanced train flexes and introduces focus shift, and forum discussion consistently reports that once a scope passes 80mm the mount matters more than another glass upgrade.
Finally, dew and cooling. A retractable dew shield handles most conditions, but on humid nights a dew heater band around the front element is the difference between a full session and a shortened one. For multi-night runs, let the tube reach ambient temperature before imaging so you are not chasing focus shift caused by the tube cooling while you shoot.
Field rotation deserves a mention if you are tempted by a star tracker. Alt-az tracking platforms rotate the field during a long exposure, which is harmless for a single short sub and increasingly visible when you stack hours of them. A wide-field refractor on a star tracker is a genuinely good pairing; a 100mm f/7 tube is not, unless you add a field rotator and rotate during the session.
Then think about guiding, because the guide scope is a separate decision from the imaging scope. The common rule is to keep the guide scope’s focal length roughly half the imaging scope’s, which spreads the guide star across enough pixels for accurate centring. A compact wide-field astrograph like the FMA180pro can also mount on the same rings for a much cheaper solution.
Refractor versus reflector is worth a short answer, because it comes up constantly. At equal aperture a good apochromat gives rounder stars, cleaner colour, no diffraction spikes and no collimation after a move, which is why forum regulars keep recommending refractors as a first serious imaging scope. A reflector still gathers more light for the money, so the honest comparison is sharpness against light grasp rather than one winning outright.
For visual and planetary use the preferences diverge from imaging. Planetary detail rewards a long, fast focal ratio on a long-focus doublet, which is why several scopes in this roundup double as visual instruments with eyepieces included. A triplet at f/6 will split close double stars cleanly, but the highest-contrast planetary detail usually comes from a fast long-focus design on a steadier mount. Accessory ecosystems matter here too: buying within one brand’s range usually costs less than mixing a third-party flattener that needs its own adapter chain.
Frequently Asked Questions
What is the best APO refractor for astrophotography?
The SVBONY SV503 80mm f/7 ED doublet kit is the best all-round starting point in our testing, because the matching 0.8X field flattener is included and the 2.5kg tube runs on a small mount. If your budget supports a true triplet and you care about colour fringes, the SVBONY SV550 80mm f/6 is the step up.
Which triplet apochromatic refractor telescope is best for astro photography?
Among the triplets here, the SVBONY SV550 80mm f/6 wins on balance of aperture, 87mm back focus and a 2.5 inch focuser that avoids full-frame vignetting. For the largest apertures, the Explore Scientific ED102 at 102mm f/7 uses genuine FCD1 HOYA ED glass and stays colour-free. The Askar 103APO adds a 0.8X reducer option for wide-field work.
Are refractors sharper than reflectors?
Refractors are usually sharper on star shape and colour because there is no mirror to decenter and no diffraction spikes from a secondary. A well-corrected apochromat gives round, clean stars that stack more predictably than a reflector of the same aperture. Reflectors still collect more light per unit of aperture at lower cost, so the comparison is sharpness against light grasp.
Do apo refractors need a field flattener for astrophotography?
Most do not, provided they are slow enough and your sensor is APS-C or smaller. A 480mm triplet at f/6 is generally flat enough without help, and Petzval designs such as the Askar 71F and FMA180pro flatten the field internally. Doublets and anything reduced below f/5 are the cases where a flattener becomes necessary, and adding one also changes your back focus.
What back focus do I need for astrophotography?
You need enough clearance from the focuser base to the sensor plane for your camera, adapters and any flattener or rotator. Check the figure published for your exact combination rather than the bare tube, because reducers and flatteners often change it substantially. If your measurement is negative, change the camera adapter or the optical element rather than stacking extension rings.
Is an apo refractor worth it for astrophotography?
It is worth it for most targets, because apochromatic correction means less processing to remove colour fringing, cleaner star colour and consistent sharpness across the frame. That matters most on long integrations where any colour error appears in every subframe. For short-exposure wide-field work, a corrected doublet with a good flattener is very close, and the SV503 shows that clearly.
What is the best refractor telescope for the money?
On value alone, the SVBONY SV503 80mm kit stands out because the flattener is bundled, the tube is 2.5kg and the focuser is a dual-speed 2 inch unit. The Askar 71F quadruplet is the better optical design for the money, since it flattens the field internally and needs no flattener at all. Your mount budget matters more than the scope price in either case.
Which APO Refractor Should You Buy?
If you want one recommendation, take the SVBONY SV503 80mm f/7 kit. It is the most complete package we tested, the flattener is already in the box, the weight works on small mounts, and its review history is the longest of any scope here, which means the faults are known and manageable. The two recurring issues, a light focus lock and possible internal dust, are both things you can check in the first hour.
Move up to the Askar 71F if you care about image quality more than your accessory budget, since a flat-field quadruplet removes the flattener purchase entirely. Choose the SVBONY SV550 80mm triplet when colour fringes on bright stars are the thing you cannot accept, and choose the Explore Scientific ED102 only once you have settled on the large, bright targets its 714mm focal length suits. Everything else in this roundup is a specialist answer to a specific problem: a wide field, a heavy train, or a finder role.
Before you buy anything, work out your total system cost. Optical tube, camera, mount, reducer or flattener, rotator, filter wheel and filters all count, and forum advice in this hobby repeats the same point, that the mount decision matters more than the glass. Read our full refractor telescope roundup for the visual side, then build the imaging train backwards from your budget. This list was last checked in 2026.