is this safe?

is it safe to have a 600watt HPS, my 4 inch exhaust/carbon filter, and my tower fan all running through the same timer from the wall through a 4 way plug?
cheers

Figure out the max Amps the timer is rated for, then use Ohms law (Voltage x Amps = Watts or in your case Watts / Voltage = Amps) to figure out how many amps you're drawing. As long as you're using at or less than 75% of the rated amps you're alright. Or if you're not the math type, just put your hand on the timer and see if it's warm/hot. If it is you're probably pulling too much through it or you're near it's capacity.

Another concern is whether or not the circuit all of this is on has other stuff on it as well. Too much will trip your breaker or cause a fire if the breaker and wiring are mismatched.