I haven’t used one myself, but from what I’ve heard about Mercury Vapor Lights, they tend to get very, very bright. Just as a heads up in case you use it at your house, as your neighbors may not be pleased.
I used the one from bioquip.com. It is a 175 watt and draws the insects wonderfully. It’s expensive, but the ballast is the part that costs most if bought individually. We use mercury vapor lights regularly, it’s best not to look at the light directly, Photographs come out green, so it’s best to have a regular light source during photography. I just use a headlamp.
I’ve recently bought a metal halide lamp from amazon, it came with a 400 watt ballast. Not great at knowing electrical things, so don’t know if that ballast would work for both. I haven’t tried out the MH yet, but one of our folks has one and it’s super bright. Happy hunting!
It draws in all sorts of insects quite well. It puts out 10,000 lumens with 200 W. It doesn’t get nearly as hot as my old metal halide lamp, so it is much safer.
125W MV bulbs have traditionally been used where mains power (or generators) are available. Although higher wattage bulbs are available a 125W bulbs can catch 100s, indeed over a thousand, moths. My own observations suggest a 250W MV only catches an extra 20% of moths, so I would just stick with the 125W. (I would avoid the self-ballasted bulbs which I won’t discuss here.) The trap design and capacity is probably more important. As kemper says they are very bright in an urban or suburban garden.
If budget is a consideration don’t forget to take into consideration how much power those high-energy ones use if you plan to have them on for any length of time. I’ve seen a couple of people recently who bought them and got shocked by the running costs. A 400W lamp is equivalent to running around a dozen 32" flatscreen TVs simultaneously.
if you are looking for a transportable moth light (too) I can highly recommend LepiLED - runs on a powerbank and while the quantity of insects attracted might decrease a bit, given that one does not need to worry about power source, and can be placed in the best habitat available
The 400W MV lamps I’ve seen in the field are exceedingly bright to the point that they light up large area (a field, neighborhood, etc.). As with all MVs, they get very hot…dangerously so. Due to their brightness, such a light can fry the sensors if you inadvertently turn a camera towards to light at close range for more than a fraction of a second. I’d stick with 175W or 250W.
I have several friends that had been using a custom designed LED from Germany. It is definitely not cheap, but it is apparently far more portable (with a battery pack) and much less prone to breakage than MV bulbs. https://www.gunnarbrehm.de/en/lepi-led
I use a 175w self-ballasted bulb, and that has been great for bugs. But the neighbours aren’t always thrilled with the light pollution.