If you already have a MagicShine headlight, pick up their taillight. It's about as bright as the low end Dinotte, definitely visible in the daylight easily from far away, and is $30. I think it's about $65 if you have to buy it with its own battery pack, but that's still cheaper than most lights of that brightness and run time.
1/2 watt is nowhere near bright enough. I don't think 1 is either. 2 is getting there. The MagicShine is 3 watts and is the low end of what I'll ride with these days. At night I run that steady and a Cygolite Hotshot on my helmet in rapid flash. In the daytime I run just the Magicshine on flash.
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Work: the 8 hours that separates bike rides.