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68g £38.99

The Moon Shield X Auto 150 Lumen Rear Light is a nine mode rear safety light with decent output, generally sensible settings and some lovely touches. However, more is not necessarily better when it comes to lumens. 80 lumens proved overkill for most contexts. I would’ve preferred 60 and longer run times.


Like many at this price point, it features a single Cree diode, projected through a sophisticated collimator lens. The Comet X auto runs an XP-E, flanked by another 20 piece COB LED unit. A rugged CNC machined aluminium heat sink offers good physical protection and disperses heat, ensuring diodes stand the best chance of a long and productive life, although this is determined somewhat by the 3.7V 700mAH lithium polymer battery.


Depending on how intelligently it’s run and charged; Moon say to expect between 300 and 500 charge cycles, or around three years.  Talking of which, there’s an inbuilt cut off to prevent overcharging and a full mains charge takes two hours-to the second, although add another 15-20minutes if its guzzling from PCs/ laptops. 


Tumbling reserves sees the light automatically kick down to the lowest, 15lumen flashing mode, which is a lot brighter than the numbers would suggest. Having run the 60 lumen shield for several seasons, occasionally mounting it to the base of a helmet, I wouldn’t recommend anything higher than the 30 lumen flash around town, since it can be very harsh at close quarters. 

Besides, when fully juiced, the 15lumen flash has lasted 29hrs and 51minutes, potentially a fortnight’s worth of middle distance commuting between charges.  As an emergency, Moon say to expect an hour between selecting the lowest setting and being truly spent-pretty accurate so far. 


Powering up is simply a question of holding the rubberised switch for two seconds, whereupon it springs to life. The memory function is great if you’ve just left the café, or have a favourite but quick double presses are all that’s needed to cruise through the settings.


Four steady, four “flashing”; five if you include the 150 lumen daylight mode. Before, I get to these a quick word about the “Auto” function. Not a completely revolutionary concept; dynamo switches have had sensors that detect and automatically turn the lamps on/off for some time.


However, it’s a rare on blinkies. Part of me says gimmick but it’s a boon when you’re out on a long autumn afternoon ride and before you know it, dusk has arrived. This option requires a constant, three second press to set but assuming the battery’s not running low on juice, resumes your last choice. 


80 lumens, whether steady, or flashing is overkill in most contexts. Admittedly, the former has come in handy along some pitch black, misty lanes-we reckon visible to around 150 metres but 1hr 16, maybe a minute or either side-tops! Flashing returned a very competitive 6hrs 52 and was arguably sufficient for daylight duties. 


That said; it’s decidedly anti-social at close quarters, hence I wouldn’t dream of running it in a group, or suburban settings. Friends following me along eerie lanes reckoned they could pick me out at ¾ mile ahead! 


50 lumens is still mighty potent  and  will return almost the two hours quoted from a full charge but 30 and 15 lumens are a lot brighter than numbers suggest. 15 consistently returned 6hrs 22-perfect for long group rides. 30 has more punch and my default for semi/rural contexts and been within 6 minutes of the 3hrs 30 quoted.  


The other flashing modes, 35 lumens apiece are quite different but come in handy around town as we gear up to Christmas and its easy to become drowned out by competing neon. 


Much of the difference boils down to pulsing speed. Flash 2 is intermittent and delivered 14hrs 56 from a full charge-four minutes short of the 15hrs cited. I found it really effective but felt safer paired with a second light in a 15lumen constant setting. Flash 4 is quicker but we are talking 6hrs 25minutes or so before its exhausted.    


Though less significant on the open road, peripheral bleed is excellent. In common with its “strip-light” shaped Comet X sibling, this produces a broad 210 degree arc of light, which anecdotally, seemed to encourage wider passing distances from approaching cars and vans. 


The whole unit is water resistant to IPX4; I would’ve preferred IPX6 or similar but heavy rain and quick blasts from the garden hose haven’t made any impression to date.

Moon Shield X Auto Rear cycle bicycle light
Moon Shield X Auto Rear cycle bicycle light beam shot
Moon Shield X Auto Rear cycle bicycle light
Moon Shield X Auto Rear cycle bicycle light seat post mount
Moon Shield X Auto Rear cycle bicycle light

Moon offer a very comprehensive fitting kit, which includes a saddle rail option and though sometimes a little too tenacious, the clothing clip has a vice-like grip - even on slippery fabrics such as winter-weight polyester training jerseys. Subjectively, I’ve really enjoyed the Shield X Auto and would recommend a closer look if the majority of your riding is along unlit roads but you wanted a design that would still cut it in town. 


Performance is certainly equal to others in this price bracket, such as Cat Eye Rapid X. That said; if this isn’t your priority, there are plenty of very capable units for £20 or less offering excellent peripheral presence and better run times between charges. 

Verdict: 3.75/5 Impressive light with output to match but best value for long rides along unlit roads.

Michael Stenning





Ryton On Dunsmore

Coventry  CV8 3FH


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