“as far a light burn, put your hand there if it is too hot for your hand it is too hot for your plant”
Lightburn has nothing to do with temperature.
Lightburn is caused by an intensity of light that is too high for your plant. We’re talking photosynthetic photon flux density (PPFD). PPFD measures the amount of PAR that actually arrives at the plants. PAR is photosynthetic active radiation. PAR light is the wavelengths of light within the visible range of 400nm to 700nm which drive photosynthesis.
PPFD is a “spot” measurement of a specific location on your plant canopy, and it is measured in micromoles per square meter per second (umol/m2/s).
Here’s an example of what PPFD you want to aim for during:
Propagation: 200 - 300
Veg: 300 - 600
Bloom: 500 - 1200
You can consult your light manufacturers website to find a chart that shows what PPFD readings they get at which height, if you don’t have a PAR meter (they’re quite expensive)