You can use just one timer connected to a Sentinel HPH-8 High Power controller to control up to eight HID light systems at the same time! 

A great solution when you're growing with multiple HID (High Intensity Discharge) lighting systems! The HPH-8 High Power HID Controller will handle eight grow lights with a combined total of 8000 watts when using 240-volt, and up to 4800 watts total usage if you're using 120-volt equipment.

It has 8 "universal" electrical receptacles that accept either 120-volt (Nema 5-15P) or 240-volt (Nema 6-15P) power cords, so there's no worry about upgrading from 120V to 240V down the road - the HPH-8 will handle the change without further investment.

The HPH–8 is housed in a sealed, aluminum heat sink enclosure and can be securely mounted using the wall mount bracket provided. Heat from the relay and internal components is radiated outside the enclosure to ensure cooler operation for long life.

Specs:

Trigger cable: 120-volt, Nema 1-15
Main Power: 50-amps @ 240-volt AC
Maximum HID wattage: 8000 watts (on 240-volt) - 4800 watts (on 120-volt)
Maximum number of HID ballasts: 8
Weight: 13 lbs
Dimensions: 7.37" long x 5" high x 10" wide
Life Expectancy: > 10 years

Carries a manufacture 3-year warranty.

You'll need to provide a 240-volt, 50-amp circuit for the HPH-8, plus a timer or a controller like the MDT-1. A pre-wired 15' trigger cable makes connecting your timing device simple.

NOTE: Installation must be completed by qualified electrician. Installation must be done in accordance with state and local electrical codes.

More info (PDF format)