can i run multiple lights off one ballast

hi i know this is prob a very stupid question but if this could be done it would make mess and heat that is created by multiple ballasts but makes me wonder is there a way i could run multiple lights off one ballast like getting a 600w and running x2 250w lights off it and having a transformer or some sort of limiter to stop more than 250w traveling through to the light

i plan to grow in my roof i have a hell of alot of wasted room up there and perfect stealth being in the roof just want to keep the whole thing tidy up there

thought i would clarify im looking at digital dimmable ballasts so i can drop it down to 500w

Here's what I have seen. http://www.ebay.com/itm/HPS-MH-Bulb-Splitter-Digital-Ballast-1000-Watts-2x600-SPLITTER-SOLISTEK-/291598846670?hash=item43e4a54ace:g:PuIAAOSwv0tVNp5N
It runs 2 600 watt @500 watt off of a 1000 watt ballast.

Yes you can. but get it and your idea checked with a local electrician first,

tho you location is not the best for growing in lofts you can get huge temperature swings

and if you are concerned with the heat now, whats it gonna be like on a hot day

best to locate to the cellar/basement stable temps and even less FLIR

or use an LED ...?