Astro-Tech AT150EDL 150mm f/8 FCD-100 ED Doublet Refractor
Big Refractor Performance — Refined, Reliable, and Ready to Deliver
The Astro-Tech AT150EDL isn’t just the largest aperture model in the acclaimed EDL series — it’s the culmination of everything we’ve learned about making high-performance refractors that deliver honest, uncompromising optical quality without the pretense of inflated pricing.
We built this telescope for serious observers, dedicated imagers, and those who demand an instrument that stands as both a practical tool and a precision optical achievement.
If you’ve been dreaming of a 6" refractor, but have been turned off by the weight, cooldown times, or price tags of triplet designs, the AT150EDL might just be the refractor you’ve been waiting for.
Optical Design — More Than Just Numbers
At the heart of the AT150EDL is a 150mm f/8 air-spaced ED doublet lens designed around Ohara’s finest FCD-100 extra-low dispersion glass. We paired it with a Lanthanum mating element — a rare choice that significantly reduces residual chromatic aberration and spherical error while maintaining a high Strehl ratio.
We guarantee a minimum 0.95 Strehl.
Why Strehl Ratio Matters
When you invest in a high-end refractor, you’re not just paying for glass — you’re paying for precision. The Strehl ratio is one of the clearest ways to measure that precision. A Strehl ratio of 0.95 or higher means the optics deliver 95% or more of the theoretically perfect image quality.
In practical terms, that translates to:
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Sharper, tighter stars
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Superior planetary contrast and detail
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Better control of aberrations like spherical error or astigmatism
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Images that hold up at high magnification without breaking down
A premium Strehl ratio ensures your telescope isn’t the limiting factor in your viewing or imaging. It’s your assurance that the optical figure, polish, and alignment meet exacting standards — letting you see all the performance your telescope was designed to deliver.
Unlike conventional ED doublets, pairing the FCD-100 with Lanthanum pushes the AT150EDL into color correction territory so tight that, for most visual observing and even imaging, it performs virtually indistinguishably from true apochromats costing thousands more.
As one Cloudy Nights reviewer wrote:
"I lined this up against my triplet and was genuinely surprised. The color correction is that good. This is a real refractor — not a compromise."
Multi-Coatings, Blackened Edges, and Light Control Baffles
We didn’t stop at glass selection. The AT150EDL features the latest generation of broadband multi-coatings on all four air-to-glass surfaces, delivering high light transmission and excellent contrast. The coatings are so effective you’ll barely see your reflection in the objective.
Inside, a system of knife-edge baffles lines the optical tube, while micro baffles run the full length of the focuser drawtube — all designed to eliminate stray light and maximize contrast. The objective lens edges are hand-blackened for added control.
Collimatable Lens Cell — A Serious Feature for a Serious Scope
We believe collimation shouldn’t be a privilege reserved for exotic triplets. The AT150EDL includes a precision-machined, collimatable lens cell — a feature that lets you ensure your scope is always delivering peak performance. Whether factory set or owner-adjusted, it’s your guarantee of optimal alignment.
The 3.2” Rack-and-Pinion Focuser — Engineered for the Load
One of the most frequent questions we hear: “Is the focuser strong enough for my gear?”
The answer here is an unequivocal yes.
The Astro-Tech AT150EDL features a true 3.2" rack-and-pinion focuser, the same robust design used on our flagship EDT triplets.
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Dual-Speed Microfocusing with 10:1 reduction lets you dial in exact focus, critical for both high-power visual work and astrophotography.
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125mm of Drawtube Travel, marked in 1mm increments, means you’ll have ample back focus (150mm total) for visual or complex imaging setups.
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Camera Angle Adjuster (CAA) built in, so you can rotate your camera or diagonal without changing focus.
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Compression Ring Holders in both 2” and 1.25” sizes protect your accessories from marring while holding them securely.
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Solid Focuser Lock ensures your imaging train stays right where you set it.
This isn’t a Crayford. It’s a geared rack system built to support heavy imaging trains, filter wheels, and the heaviest of visual setups — without slop, flexure, or shift.
As one Cloudy Nights user put it:
"This focuser alone is worth half the price of the scope. It’s buttery smooth and holds my entire imaging rig without a hint of slip."
Built Like a Workhorse, Handled Like a Thoroughbred
A 6" refractor should inspire confidence — not fear of setup.
The AT150EDL optical tube weighs 20.5 lbs on its own. Add the precision CNC rings, Losmandy dovetail, and our ergonomic CNC carry handle, and your setup comes in at 25.05 lbs total.
That’s well within the working range of premium mounts like the iOptron CEM70, Losmandy G11, and even the Paramount MyT. You’ll enjoy rock-solid stability without the burden of needing a massive observatory-class mount. You could go smaller like the Celestron CGX as well without issue.
The retractable dew shield reduces weight and bulk while keeping the optics protected from stray light and moisture. The overall length of the scope with the dew shield extended is 43.5”, making this a large but manageable optical tube for both home and field use.
Supplied Accessories — Because You Deserve the Full Package
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Hard-Sided Carry Case included for secure transport and storage.
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Losmandy D-Style Dovetail & CNC Tube Rings provide a solid, flex-free mounting solution.
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CNC Carry Handle makes setup a breeze.
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Vixen-Style Finder Shoe on the focuser for your preferred finder.
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Slip-On Metal Dust Cap protects your optics when stored.
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4" Removable extension allows the user to gain some extra "space" when using items like a binoviewer
Performance in the Field — The 150mm Sweet Spot
The AT150EDL hits a performance sweet spot few telescopes can claim. With 150mm of aperture at f/8, you’ll enjoy bright, sharp views of planets, split tight double stars with textbook diffraction patterns, resolve detail in globular clusters, and take in richly populated open clusters with contrast and clarity.
For astrophotographers, the moderate focal length delivers versatility — with excellent field correction when paired with the right flattener or reducer. The long back focus ensures compatibility with a wide range of imaging accessories.
Cloudy Nights Community Says:
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“Everything I wanted in a 6” refractor — without the triplet price tag.”
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“A legitimate visual scope and a capable imager. The focuser is a beast.”
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“Best doublet I’ve ever owned, hands down.”
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“Finally, a big refractor with a collimatable cell and a serious focuser.”
Observing Tip — Why a 6” Refractor Matters
A 150mm refractor represents a threshold in amateur astronomy. It’s large enough to take full advantage of steady skies for high-power planetary work, yet versatile enough to excel on deep-sky targets. You’ll split doubles you thought were impossible and see lunar detail with a sharpness that’s only possible in high-end refractors.
Final Thoughts — The Refractor That Earns Its Keep
The Astro-Tech AT150EDL isn’t a “showpiece” scope to sit unused in a collection. It’s a true observing and imaging tool — crafted with care, engineered for longevity, and priced for real-world astronomers who demand excellence from their gear.
Like a precision timepiece or a finely tuned sports car, the AT150EDL doesn’t just look the part. It delivers, night after night, year after year.
