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Comparison — LED Nautilus MKII and Halcyon Focus 2.0
Both lights belong to the same class: adjustable beam, canister battery, technical diving. They differ in their engineering premises — and that shows up in the numbers.
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Let us start with the most important point for good order: all Halcyon Focus 2.0 data in this article come from specifications and descriptions published by the manufacturer and its distributors. We are not comparing impressions or opinions, only the figures each side declares. Where our measurement method and theirs may differ, or where the manufacturer does not state a figure, we say so plainly.
Specification table
| Spec | LED Nautilus MKII | Halcyon Focus 2.0 |
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| Light source | 1 × Luminus SFT-70.2 LED | LUX engine, LED type not stated |
| Optics | Short focal Fresnel lens | Two reflectors + Fresnel lens |
| Intensity (1 m) | 92,000 Lux | 80,000 Lux |
| Intensity (5 m) | Not stated — we measure at 1 m | 1,550 Lux |
| Luminous flux | Up to 3,200 lm | Not stated in the specification |
| Beam angle | 4.7–60°, continuous | Fully adjustable, angles not stated |
| Head power draw | 30 W | Not stated; 15% draw on low |
| Standard battery pack | ACCU Type 9 — 9 Ah Li-ion | 5.2 Ah |
| Battery options | ACCU Type 9 / 14 / 24 | Per manufacturer’s range |
| Burn time, max. output | 3h 00′ (Boost, ACCU Type 9) | ≈2.5 h (HIGH) |
| Burn time, min. output | 12h 00′ (Operational, ACCU Type 9) | ≈5 h (LOW) |
| Output levels | Boost / Operational / Back-up | HIGH / LOW |
| Beam adjustment | Magnetic clutch ring | Mechanical adjustment |
| Head construction | Unicase — solid aluminium block | Three sealed sections: LED, driver, cord |
| Thermal control | Active, with sensor | Not stated in the specification |
| Reserve mode | “Take Me Home”, over 1 h | Not stated in the specification |
| Weight | 366 g — head, in air | 1.3 kg — complete light |
| Cord | E/O cord, sidemount versions | Standard or detachable E/O |
| Handle | Goodman handle, light handles | Adjustable, right and left hand |
| Max. depth | 150 m | Not stated in the specification |
Halcyon Focus 2.0 data — per the manufacturer’s and distributors’ specifications. Ammonite System data — own measurement, fully charged battery pack.
The same optical idea, a different execution
It is worth starting with what both lights have in common, because it is not a coincidence. In the Focus lights Halcyon uses a LUX engine: two reflectors and a Fresnel lens which together collect the light into a concentrated beam and markedly reduce energy consumption. We take the same route — a short focal Fresnel lens instead of a classic reflector. Fresnel optics are the standard in this class of lights today, not a differentiator.
The difference lies in what the lens has to collect. In the MKII that is a single Luminus SFT-70.2 LED with a very small emitting surface. The smaller the emitting surface, the tighter the optics can collect the light — and that is how we got down to a 4.7° cone.
Intensity: 92,000 lux against 80,000
Halcyon states 80,000 lux at 1 metre and 1,550 lux at 5 metres for the Focus 2.0. The LED Nautilus MKII gives 92,000 lux at 1 metre. At the centre of the beam, at one metre, that is about 15% more.
The MKII’s nominal luminous flux is up to 3,200 lm and is not the highest in this class; that is a deliberate choice. Underwater what counts is not the total amount of light leaving the lamp, but how much of it reached the point you are looking at. Light sent outside the cone comes back to your eyes in silt as a milky glow.
Lux, not lumens, decide whether your buddy sees your signal from the far end of a compartment. |
Energy: 5.2 Ah as standard against 9 Ah as our entry point
The Focus 2.0 comes as standard with a 5.2 Ah battery, which according to the manufacturer gives about 2.5 hours of burn time on high power and 5 hours on low. On the lower light level, energy consumption drops to 15%.
Our smallest option is the ACCU Type 9, that is 9 Ah. Above it sit the ACCU Type 14 and ACCU Type 24. On top of that, the MKII head draws 30 W instead of its predecessor’s 40 W, and the light levels on the magnetic switch were re-set for economy.
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Nautilus MKII / ACCU Type 9
12 h
Operational
3 h
Boost
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Halcyon Focus 2.0 / 5.2 Ah
5 h
LOW
2.5 h
HIGH
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The names of the output levels are not equivalent — this sets the highest and lowest level of each light side by side.
Beam range: 4.7° to 60°, stated as a number
Halcyon describes the adjustment on the Focus family as a fully adjustable beam letting divers move from a concentrated beam to the wide lighting used for photos and video — without stating the angles. We state the range as a number, because we believe a diver should be able to compare it: 4.7° spot, 60° flood, continuous adjustment, no modes and no steps.
The focus ring runs on a magnetic clutch. There are no knobs and no thread that could seize with grit, and the resistance is noticeable through a thick dry glove. The whole range is covered with one movement of the hand.
Thermals: Unicase and active thermal control
Every powerful LED head has to send its heat somewhere, and this is where the paths diverge. The Focus 2.0 is built from three sealed sections that isolate the LED unit, the driver and the cord from each other — a solution aimed at sealing and section-level serviceability. In the MKII the LED body is CNC-machined from a single block of hard-anodised aviation aluminium; we call that construction Unicase. With no bolted joints in the heat path there is less thermal resistance, and a housing that stays in direct contact with the water works as an instant heat sink.
On top of that comes active thermal control: a sensor monitors the LED continuously and, as temperature rises, output is reduced when necessary. This protects the LED from damage and stays practically unnoticeable to the diver.
Modularity: a light against a system
This is a difference of philosophy, not of a single specification. The LED Nautilus MKII is part of a system: heads, E/O cords, battery packs, handles and mounts are chosen separately, and a battery pack bought once will serve the heads that follow. ACCU THERMO packs go further — one canister powers a 12 V light and heated undergarments at the same time, with three-stage heat control operated by a large magnetic switch in thick gloves.
Service follows from the same principle. Every part can be replaced on its own, and the equipment is designed and manufactured in Poland from machined aluminium and Delrin.
Which light to choose
Highest intensity and the tightest spot — the MKII gives 92,000 lux and 4.7°, both stated as numbers. |
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Long dives and decompression — 9 Ah as the smallest option, 14 and 24 Ah above it, at a 30 W draw. |
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Heating from the same canister — ACCU THERMO packs power the light and the heating together, up to 200 W total load. |
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A travel light — the Focus 2.0 weighs 1.3 kg complete, and the 5.2 Ah pack is smaller and lighter than our smallest canister. If two and a half hours on high is enough and luggage weight matters, that is a real advantage. |
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Presale now open — limited time offer
Head, battery pack, cord and handle are chosen separately, so you build the set around your diving rather than around a catalogue. A limited-time presale is currently running on our website with an attractive discount, on both the standalone LED Nautilus MKII head and complete systems with ACCU canisters, cords and chargers. Build your system |
Halcyon and Focus are trademarks of Halcyon Manufacturing, Inc. Ammonite System is not affiliated with that company. Competitor data quoted for information purposes only, per the manufacturer’s specification available on the date of publication.
