Moon Nebula rear light

The Moon Nebula's 100-lumen highest mode (steady and flashing) is arguably overkill save for really foggy conditions, but thankfully the size, diode distribution and wealth of alternative settings on offer keep things practical in pretty much every riding context.

Using Chip on Board (COB) technology, Moon has loaded the Nebula with 50 diodes and eight (four steady, four flashing) modes to choose from. These feed from a 3.7-volt 800mAh lithium polymer cell, which mains charges in a very competitive (and office-friendly) two and a half hours. The battery life indicator is pretty intelligent, giving plenty of opportunity for clicking down to conserve power.

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Constant modes are: low (15 lumen), standard (30 lumen), high (45 lumen) and overdrive (the full 100 lumens). Flashing follows a similar narrative: 10 lumens, 50 lumens and 100 lumens, plus strobe, which is a town-sensible 20 lumens. A memory function ensures you can default to a favourite setting.

The lens uses collimators to project a very precise and pure 270-degree arc of light, which tends to reinforce your presence and encourage a wide berth from overtaking traffic.

A CNC machined heat sink dissipates heat build-up.

Moon says the Nebula meets IPX4 for water resistance, which is heavy rain. I've had no problems to date, even when washing bikes with the light in situ. The USB port plug fits very well and, positioned vertically, is out of harm's way.

Switch

The switch is very small and trickier to locate than some, especially in the dark and when wearing full-finger gloves. It requires a definite prod to bring the unit alive, and I'm yet to experience an unwanted power-up.

Mounting options

Moon's mounting hardware is among the most comprehensive I've come across and even includes a saddle rail bracket as well as trailer tubing and seatstay options. Provided you've wrapped the rubber tight enough, there's no hint of the light wandering.

Aside from the obvious seatpost mount, I've tended to opt for the clothing clip, which is super-tenacious whether tethered to a jersey pocket or dedicated tabs on jackets/luggage.

Performance

Starting at the top, the 100-lumen settings are unmistakably bright, though not uncomfortably so during the day. Depending on lighting conditions, I'm told it's obvious at 200 metres, dipping to 100 or so from the side, at T junctions or roundabouts.

Crucially, it's assertive rather than aggressive, so approaching traffic doesn't get an eyeful. That said, some riders commented they wouldn't want to be following it at close quarters on a group ride.

Daylight aside, I've not felt the need for such a high setting. I can appreciate its value in brief sections of thick fog, but beware it'll also drain the battery in just over an hour.

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When it comes to social riding, the low steady or 10-lumen flashing options are arguably best. Both are very obvious from every angle. Even allowing for other light pollution, a couple of riders drawing beside me at the lights reckoned they could pick me out from 150m.

Low is reckoned to return 7:30 from a full charge. I've managed 7:21, which is close enough, allowing for the fact that I'd changed modes a couple of times during that phase.

The 10-lumen flashing mode wouldn't be my first option for long stretches of unlit road, but run-time is excellent, 20:33 – within 7 of that cited.

As my sole source of rear lighting, say on an all-nighter, I'd go for the 20-lumen strobe. The general consensus suggests I came on most people's radars at 180m, maybe a little further on crystal clear nights and dipping slightly in town.

Used with other more powerful lighting when towing a tagalong/trailer, strobe has seemed up to the job for the suburbs/outskirts of town without being too brash in stop/go traffic. Beyond, I've been inclined to click over to 50% flash. Even on my low-slung Bob Yak homage, the average driver seemed to take notice at 225m, and better drivers calculated the additional length when overtaking.

Conclusion

The Nebula gives scope for pretty much every condition, has ample presence and good run-times. That said, while I've been grateful of the 100 lumens in very specific contexts, I'd suggest it's generally more than most of us would need.

Verdict

Very powerful but generally usable rear light with sensible run to charge ratios