some low wattage HPS ballasts are also capable of running MH, the smaller HPS ignitor has enough ass behind it it can safely send a high voltage pulse to start the MH.
the bigger the MH lamp, the more risky this operation is. if you move up into the 400w class, the ballast will have to have a separate ignition circuit to run the MH lamps, there also known as selectable output ballasts. Your ballast is not selectable output, but like i said, the ignitor has enough 'ummmmmpf' behind it to work. Long term operation of a non selectable output HPS ballast with a MH lamp will shorten the lifetime of the MH lamp. Basically, it causes blackening of the arc tube on the MH lamp, which degrades heat radiation, which in turn causes excessive heat buildup inside the glass encapsulated arc tube, which, over time, causes premature lamp failure. Its something that happens over months, not days, so its hard to notice. that makes it dangerous, because when an HID lamp fails due to excessive heat, more often than not, it explodes. that is why there is a capsule within a capsule in every HID lamp, if that lamp blew with just one layer of glass, the sudden exposure to oxygen of elements burning @ 4 times the surface temperature of the sun, explosions happen.........
