Happy new year to all & let me wish every one a very successful 2012 as we've all survived the challenges of 2011. I would like to convert an "advertising in motion Display Unit" from a now defunct business  re: photo attached to an exposure unit / Light box. The unit is 24" x 36" it has a control panel which contains a timer unit for exposure of  images. All I've got to do is disable / remove the spools on either ends of the unit & install  f20t12bl tubes. Presently I have 8 f20t12bl fluorescent tubes for installation but intend to increase the number to 12 later. However I have a problem with the ballast requirement for such a venture;  I have a number of ballast spares on hand but I do not know whether they are compatible with the f20t12bl  tubes I have. Your comments & suggestions are welcome, please advise.

P.S I've resized the attachments as the file files were to large, sorry the information on the ballast is now illegible hence I will not include the photo of the ballast. However the following are  the spec on the ballast: CLASS P 8G1185G11, 120 volts, 60HZ, .70 AMPS. It also has the following: For use with one FC16T9/RS or one FC1279/RS 430 MA Lamp.

Ballasts aren't too expensive, any home improvement store should have what you need.  You didn't mention the thickness of the glass.  Is it thick enough to put weights on top of your screen to prevent light scattering?  I built my first exposure unit and used a digital control panel from a microwave oven (just a suggestion).