A question I get a lot is: what lights should I be using. Can I use a 600 hps for veg as well as flower?
Yes you can
I answered this very question last night. Just make sure you keep the lamp at least 32" or more above the plants when they are young.
Best way to judge if lamp is too hot, or too close to the canopy; Hold your hand flat, palm down at the canopy. You want to feel a slight warmth, allowing you to leave your hand there comfortably. If the back of your hand feels hot; Raise the light 2", until you find the comfort zone.
Also; It is important to have a dedicated fan blowing across the top of canopy, below the lamp in order to move heat away and circulate the air.