You're going to need something more complex than just a capacitor.
First a correction to what you wrote. Capacitors are not used inline, they are connected to a power source and a ground. When power is applied to them, they begin to store the voltage and "charge" up, when the power source is disconnected they release the voltage they've stored back to the circuit load. To say it another way, they buffer ( store ) the voltage until they are full and release it once the power source is stopped.
What you need is a timer circuit. I suspect a simple one using a 555 timer chip setup in astable mode would do what you are asking but it will take a bit of calculating to find out specifically what components you'd need. You'd need a couple of capacitors and a couple of resistors ( or better yet, two potentiometers so you can vary the time off and time on portions )... The values for the components you'll need will depend on the voltages and amperage of your circuit that is driving your strobes. If the circuit you are driving ( ie the strobes ) has a high amperage draw, you will likely need a relay also in order to switch things on/off so you don't overload the timer chip.
Here is an Instructable on using the 555 timer chip in 3 different modes ( including the astable mode )
555 Timer
Here is a video describing the basics of the 555 timer in it's various modes...