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LED Nautilus MKII — technology
The new head is not a facelift of the old one. We changed the light source, the optics, the thermal construction, the way the beam is adjusted and the control electronics.
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For years the LED Nautilus MK1 was the primary light of choice for many technical and cave divers. When we started work on its successor, we did not want to simply add lumens. The question was a different one: what in this light limits the diver most underwater? There were four answers — the width of the narrowest beam, energy consumption, head temperature, and operating knobs in thick gloves. Each called for a different engineering solution, and their sum is the LED Nautilus MKII.
1. A new light source: from a COB chip to a single Luminus SFT-70.2 LED
The MK1 ran on a Cree CXB COB chip. That is a large-emitter solution: it puts out a lot of light, but from a wide surface, and optics cannot collect such light into a tight cone. The MKII uses a single high-efficiency Luminus SFT-70.2 LED with a far smaller emitting surface.
The consequence matters more than the spec line suggests. Nominal luminous flux went down — from 4,000 lm in the MK1 to up to 3,200 lm in the MKII. At the same time the intensity at the centre of the beam went up, from roughly 65,000 to 92,000 lux at one metre. Underwater it is the second figure that counts: lumens describe the total amount of light leaving the lamp, lux describe how much of it reached the point you are looking at. In silt and poor visibility, light scattered outside the cone does not help — it comes back to your eyes as a milky glow.
A smaller emitting surface is not a catalogue detail. It is the condition without which no optics will collect the beam down to 4.7°. |
2. A short focal Fresnel lens: 4.7° to 60°, with no steps
We paired the new LED with a short focal Fresnel lens. The short focal length let us fit the whole assembly into a compact head while widening the adjustment range at both ends of the scale.
A 4.7° spot instead of 9°. An almost twice narrower beam for communicating with your buddy and for cutting through dense silt. |
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A 60° flood instead of 45°. Wider for orientation in large spaces, inside a wreck compartment and for video. |
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No steps, no modes. Adjustment is continuous — you set the beam to the task instead of picking from a list. |
3. Unicase: a housing that is the heat sink
In the MK1 the LED passed its heat into a bolted heat sink made of several parts. Every mechanical joint is thermal resistance. In the MKII the LED body is CNC-machined from a single block of hard-anodised aviation aluminium — a construction we call Unicase. Heat from the LED has one short path into the aluminium, and the aluminium stays in direct contact with the water. The housing works as an instant heat sink and keeps the head thermally stable.
On top of that comes active thermal control: a sensor monitors the LED continuously. As temperature rises, output is reduced when necessary. This protects the LED from damage and stays practically unnoticeable to the diver.
4. A magnetic clutch instead of Delrin knobs
Beam adjustment on the MK1 was handled by Delrin polymer knobs. In thick dry gloves and with cold hands, that was the most tiresome place on the whole light. In the MKII we replaced them with a ring running on a magnetic clutch. The movement is smooth and even across the whole range, the resistance is noticeable even through a glove, and there is no part in the adjustment path that could seize with grit.
Weight dropped along the way. The head weighs 366 g in air instead of 415 g — 11.8% less. On a two-hour decompression with the light on a Goodman handle, that is a difference your wrist notices.
5. The microcontroller: light levels and the “Take Me Home” mode
A more efficient LED is the first source of energy savings. The second is the electronics. The magnetic switch on the MKII gives three levels — Boost, Operational and Back-up — and we re-set the values of those levels so that the light manages energy more economically.
The microcontroller also monitors the remaining energy in real time. When the battery runs low the system first warns with a flash, then automatically switches to the “Take Me Home” reserve mode, which guarantees over an hour of additional reduced-output light for a safe ascent.
Burn times on ACCU battery packs
Power draw fell from 40 W to 30 W. Together with the re-set light levels, that gives up to three times longer burn time on the same battery packs:
| Battery pack | MK1 Operational | MKII Operational | MK1 Boost | MKII Boost |
|---|---|---|---|---|
| ACCU Type 9 | 4h 00′ | 12h 00′ | 2h 25′ | 3h 00′ |
| ACCU Type 14 | 6h 05′ | 18h 30′ | 3h 40′ | 4h 40′ |
| ACCU Type 24 | 10h 05′ | 24h 00′ | 6h 05′ | 8h 30′ |
Every change in one table
| Spec | Nautilus MK1 | Nautilus MKII | Gain |
|---|---|---|---|
| Light source | Cree CXB COB LED | 1 × Luminus SFT-70.2 LED | Higher efficiency per watt |
| Optics | Reflector | Short focal Fresnel lens | Wider adjustment range |
| Max. luminous flux | 4,000 lm | Up to 3,200 lm | Optimised for intensity |
| Intensity (1 m) | ≈65,000 Lux | 92,000 Lux | +41.5% at beam centre |
| Spot beam angle | 9.0° | 4.7° | Almost 2× narrower |
| Flood beam angle | 45° | 60° | +15° wider coverage |
| Power draw | 40 W | 30 W | 25% energy saving |
| Head weight | 415 g | 366 g | 11.8% lighter |
| Thermal construction | Bolted heat sink | Solid Unicase block | Water-cooled heat sink |
| Thermal control | No sensor | Active, with sensor | Protects the LED |
| Beam control | Delrin knobs | Magnetic clutch ring | Operable in gloves |
| Reserve mode | None | “Take Me Home”, over 1 h | Reserve for the ascent |
| Max. depth | 150 m | 150 m | Unchanged |
What this means for the diver
The MKII goes narrower when you need to show something to your buddy or see through silt, and wider when you need to take in a whole compartment. It does this at 25% lower power, so the same battery pack lasts a longer dive — or lets you move down to a smaller, lighter pack. The adjustment works in gloves, and the head is 49 g lighter.
The head keeps the modularity of the system: it runs on the same ACCU battery packs, E/O cords and handles as the other Ammonite System Primary Lights (corded). If you already own a battery pack for the MK1, the MKII will burn longer on it than its predecessor did.
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Presale now open — limited time offer
The MKII retains core Ammonite DNA: 150-metre depth rating, three-level intensity control, hard-anodised durability, and full backward compatibility with standard cords and canisters. 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. Reserve now |
Technical data refer to the LED Nautilus MKII and the discontinued LED Nautilus MK1. Burn times measured under laboratory conditions with a fully charged battery pack.
