Absolutely. I've got two MH 400w
lights made from high bay ballasts. If you follow the link below you can see a few pictures I took. I removed the lens and hanger assembly and removed the ceramic mogul socket. I bought a commercial horizontal reflector that had its own mogul socket built in. I also bought a horticultural bulb. Then I wired it all up. If you use a high bay
ballast, make sure it has 120volt taps if you plan to use it with standard wall power. I got the idea to do this from a guy on this website! Saved me a lot of money. You might be able to use the high bay reflector for more savings, but I wanted something better looking since this all lives in my florida room and I wanted a glass cover for extra protection.
Pictures here:
Hydroponics Warehouse Lights