Flourescent light bulbs are a glowing cylinder of light, not a line source of light, so there is no optimum reflector for them, and no mathematical formula for designing one. I think it is best to just do a simple line drawing of the bulb cross section (a circle), and start putting flat planes around it and ray tracing to see how they reflect. (Light reflects off a shiny mirror surface at the same angle from the vertical as it hits the reflector, so ray tracing isn't difficult. But, rays come from all over the surface of the bulb, not its centerline. Make the reflector so the bulb is up inside it far enough that you can't see the bulb or bulbs when you look up at it at the tank rim locations. That stops most of the light spillage. Then, just have fun playing with various configurations on paper. See http://tinyurl.com/dy2th4
for one possible configuration.
Don't use mirrors. Glass mirrors reflect a small percentage of the light that strikes them. You want a surface that will reflect 90% of the light, like really white paint, or shiny aluminum.
I had read your posts re: the white paint, aluminum and mirrored surfaces, very enlightening to say the least, i did as suggested and found some ray tracing software. The results after a bit of fiddling was impressive, the light source needs to sit far higher into the reflector than i had originally imagined, and also found by placing a 45* angled point at exactly the 0* point re strike was nearly totally elated on my limited layout.
I am impressed looks like a simple 6" arc with a 45* point directly above the bulb will fit the bill nicely. Surface of the bulb from the surface of the reflector will be approx 1/2" per my crude settings, will do a new layout and try and get the values closer, but dont really think that is necessary, Not looking for nth% degree accuracy here, just fully functional
Looks like so far costs are 40.00 for 2 electronic ballasts, 3.79 * 3 for the three bulb fixtures and 5.00 for 5' of 6" PVC pipe.
so i have 1 15w OD * 1.4, 1 15w NO, and 1 18W NO.
so the next question is how would you calculate WPG on a tank shaped like a diamond.
The 18W runs the full 24" side 1, 4" off the side
1 15W runs the remained of side 2 4" off the side
The OD 15w runs parallel to the front 4" off the front
I ( may be incorrect here ) used the following method, please someone chime in if this is in error, or you know of a better method.
Light 1 ( 18W ) covers an area 8 x 24 x 24
8*24*24=4608 cubic in volume /238 ( 1 gal covers approx 238CI )= 19 gal less volume taken by gravel etc of 10% 19.0 -1.9=17.1
so assuming a standard fudge factor on T8's of 1.4 * 18w = 25w/17 gal = 1.47 WPG
Light 2 ( 15w ) covers an area 8 x 18 x 24
8*18*24 = 14.5 gal less 10% = 13 gal Light output = 15w*1.4= 21w/13g = 1.6 WPG
Light 3 ( 15W OD ) covers an area 18 x 24 x 6 ( this is also the least plant populated area of the tank )
18*24*6=10.8g less 10%= 9.8g
15w [email protected]
1.4= 29.4W/9.8g= 3WPG
so left side = 1.47 WPG
right side = 1.6 WPG
Center = 3.0 WPG