OK...since you wan to try 1-1/2 feet. you must set you plants where they are going to reside...make adjusment to the height of your 250w (keep light off until you have it secured where it will ride!!! very important). You do not want shards of....how does Zandor put it???shards of 10,000 degree glass in your face...lol, NO seriously!

Once you have lamp in place plug in-turn on, wait a few minutes until the lamp is all warmed up and glowing 100%

Now place your hand...as close to canopy(top of plant) as you can get it. If the back of your hand get's hot...You are too close! move lamp up 6"...It is better to have it a little farther away and stretch a teeny tiny bit...than it is too try and get light too CLOSE & MELT THEM!!! personally, I wouldn't put a 250w closer than 2-2-12 feet to start with after thinking it through, some more. Really...nitpick on that for the night...later

lw