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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.
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.
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.
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.
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.
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.
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.
Very powerful but generally usable rear light with sensible run to charge ratios
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road.cc test report
Make and model: Moon Nebula
Size tested: 100 Lumens, 93x22x17mm
Tell us what the light is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
All Moon says about the Nebula is: "High power USB rechargeable."
My feelings are that it's a comprehensive and very powerful light with functions to suit pretty much every riding context, with decent run-times.
Tell us some more about the technical aspects of the light?
Moon lists these features:
* 1 pc (50 chips) Rectangular ring COB high brightness red LED
* CNC Aluminium heat sink casing
* Rechargeable lithium polymer battery (3.7V 800 mAh)
* Day flash mode, Mode memory function, Auto safe mode
* 4 steady modes, 4 flashing modes
* Quick release universal bracket fits all round and AERO style bars
* Low battery, charging and fully charged indicator
* Automatic fully charged cut-off system
* Side visibility
* Water resistance (IPX 4)
* Recharge time 2.5hrs
* Size (W x D x H): 93 x 22 x 17 mm
* Weight: 0.18Kg; Packing & Package: 0.1Kg
Small switch wasn't the easiest to operate, though better than size might suggest. Very positive too, so accidental engagement is unlikely.
Brilliant choice of brackets means it can cadge a lift on seatstays, saddle rails, clothing, luggage and so on. Aftermarket clamps will also fit to racks.
Rated to IPX4, which is fine for road riding. If fitting to a recumbent or a low-slung trailer, I would be inclined to put a drop of silicone grease on the port plug to be on the safe side.
Generally excellent, although I can't help thinking that the 100-lumen overdrive mode is of limited use.
High-quality LED, battery and circuitry, so with basic care there's no reason it shouldn't have a long life.
Heavier than some but mitigated by size and output.
Not cheap but not outlandish given the output, tunability and intelligent design. Could be all the rear light some riders need.
Tell us how the light performed overall when used for its designed purpose
Overall, the Moon Nebula has a wealth of modes to tackle pretty much every riding context, but feels versatile rather than overburdened. The highest (flashing) settings were visible from at least 200m, and 350-400m on very clear nights, yet the run-times are favourable, and others provide just the right balance for group riding.
Tell us what you particularly liked about the light
Great if you want a single rear light. Small and neat, yet very potent.
Tell us what you particularly disliked about the light
Nothing given the design brief. That said, I can't help feeling, save for extreme conditions, 100 lumens in overdrive (steady) isn't the optimum for a rear/safety light.
Did you enjoy using the light? Yes
Would you consider buying the light? Yes
Would you recommend the light to a friend? Yes
Use this box to explain your score
Powerful, intelligently designed light that will cope with pretty much every riding context.
About the tester
I usually ride: Rough stuff tourer based around 4130 Univega mountain bike frameset My best bike is: 1955 Holdsworth Road Path and several others including cross & traditional road
I've been riding for: Over 20 years I ride: Most days I would class myself as: Experienced
I regularly do the following types of riding: cyclo-cross, commuting, touring, fixed/singlespeed, mountain biking
Shaun Audane is a freelance writer/product tester with over twenty-eight years riding experience, the last twelve (120,000 miles) spent putting bikes and kit through their paces for a variety of publications. Previous generations of his family worked at manufacturing's sharp end, thus Shaun can weld, has a sound understanding of frame building practice and a preference for steel or titanium framesets.
Citing Richard Ballantine and an Au pair as his earliest cycling influences, he is presently writing a cycling book with particular focus upon women, families and disabled audiences (Having been a registered care manager and coached children at Herne Hill Velodrome in earlier careers)