Heat is the biggest issue with MH/CMH/HPS.
Lights are too close when you can feel the heat on the back of your hand when your hand is held at the tips of the plant. Anything else pretty much goes.
One thing to watch for when learning to place light height is node spacing. Too little light results in a spindly plant. Too much light results in an overly compact plant. Cannabis responds very well to light adjustments in terms of this. You will get a feel for it over time.
I grow with LEDs, so I can’t give guidance on specific light heights, but there are a few growers here that do. Perhaps one of them can chime in with a specific recommendation.
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