Title says "Orbit Marine Pro" :) :)
And yes, you should have no trouble with corals.
You should still get a light meter so you can have a way to judge what you're doing with the light.
Start with a free lux meter app for your smartphone. It uses the camera's light meter to generate a normal lux reading. For example, "galactica luxmeter" for IOS, but there are lots of light meter apps.
I'd also suggest ordering a $15 handheld lux meter from your favorite online reseller. Better readings and safer to use around saltwater. :)
Do you have it on the tank rim or suspended above?
If you're suspending it, you should be able to bring it up to about 8 or 9 inches over the water to get better front to back coverage at the top of the tank.