Indoor Lighting height Q

[turtle360]

From the nit pickers association, one guidance for how far away a MH light should be looks something like this:

400W 8" (15cm) 12" (30cm) 19" (48cm)
600W 9" (20cm) 16" (41cm) 25" (64cm)

Since the bulb can be 5 inches above the cover are we measuring from the bulb or the cover?

Yeah, I know. The burn your hand test is definitive. I don't relish soaking up rays waiting to find out how hot it is.

 

[Son of Hobbes]

As far as I know, those recommended distances are based on light, not heat. That's why it's recommended to use the "hand test" to make sure it's not too warm. The distances quoted may be optimal but other growing conditions can factor in, like whether it's a vented hood or open air reflector, the temperature of the grow space, air movement, etc etc.