Moon Arcturus Auto

The Moon Arcturus Auto is a super little rear light for commuting and general riding. It's useful for a variety of scenarios, with seven modes in total – two main modes each with three sub-settings, plus a daytime mode for added safety. The single button is perfect for on-the-move adjustment.

My commute isn't lit, and includes a mix of A roads and narrow country lanes. The Moon's 35-lumen modes are easily bright enough for pitch black riding, while the extra-bright 70-lumen double flash is great for daytime. This is enhanced by the Auto Mode (hence the name), which switches the light on when it senses very low light. This came in really handy when going from sunshine into heavy tree cover, giving that bit of extra safety against drivers adjusting to the light change.

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The Arcturus Auto is simple to set up, with a small bracket and just one securing band. I took it out of the box before I left for work one morning and had it on the bike and flashing in under two minutes.

It attaches to your bike via an RB-22 bracket which, helpfully, is compatible with all of Moon's other lights, making switching out lights for different situations a breeze. The Arcturus also comes with two O rings: the RS-G for 20-35mm diameters, the RS-H for 35-52mm diameters, giving a wide range of places to mount the light.

With its CNC aluminium heat sink casing and one-button operation, turning the light on while moving is very easy. Some lights have a tiny button, resulting in much under-crotch investigation, but the large button right in the centre of the Arcturus is easy to find.

The Arcturus Auto gives a spot angle of 105 degrees, which equates to a 26-metre-wide beam when 10 metres behind the light. The total angle of 270 degrees means the light can be seen by those only marginally behind you.

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Its rechargeable lithium polymer battery gives a run time of between 1:20 and 17 hours, depending on the setting. As with any light, the flashing modes retain more battery life than constant ones; constant at 35 lumens will drain the battery in 1:20, whereas 35 lumens flashing will go for 8 hours. With its USB rechargeable feature, this shouldn't cause any problems, but it is worth considering the run time of each mode; I am able to charge the light at work, but this isn't an option for everyone.

Wet commutes shouldn't have any adverse effects – I've been testing the light in relatively dry conditions, so had to simulate some heavy downpours with a hosepipe, and I can report that no water got in.

Verdict

A sturdy, well-made rear light with ample settings for day and night