It depends....If you have an air cooled hood you can go 12-18" away but if you dont have an air colled hood it will get hot and heat will be more of an issue.... You want to get as close as possible without burning the tops (heat) or bleachin/leaching the leaves ( light too close)how far away should they be fro the plant
( the lights )
yes I too have also vegged with 600. But i used a MH bulb,..... HPS will cause a little stretching when used for veggin though. And just like ghost said, put the back of your hand under the light, at the same height as the tops of the plants,.....if it feels uncomfortable, it is too close/hot.i used my 600 for veg 24/0 for 4 weeks then flowering 12/12 for 8 weeks worked well yeah def about a meter away if its to hot on the back of your hand its to hot for your girls