LED Fixture Spacing

[NatD]

Hi all --

I am getting ready to hang 4 Giesemann Vervve fixtures over a 48"x48"x18" tank.

The hangers I'm using will allow me to easily raise and lower them, but I would like to try to avoid having to move them left or right once they are up.

Since the tank is unusually shaped -- I'd like some opinions on spacing them.

My plan is below -- thoughts?

 

[oreo54]

Whats the lens beam angle?
looks greater than 90 degrees..

Are there choices?
Do you want full coverage top/bottom or sacrifice some light at the top for more PAR deeper??

Roughly speaking.. at 6" (w/ 120 degree lensing) above the water line you need the pucks about 10" from the tank side.
That should get you converging pucks(barely) in the center at the surface.
Tangent of 1/2 the beam angle will give you the radius of the cone.
Above used 10.39" for radius.. 4" for puck and 10.39 for the "other" side..
@ 90 degrees you have 6..4...6

Pucks might be 6" don't know..Need puck diameter..


Keep in mind edge light falloff is much greater than center

Once the light is in the tank is is partially "trained "by reflections off the glass..

And honestly, it will require some trial and error even knowing the answers to the above question..but can get closer..

 

[dantimdad]

Agreed. This would be trial and error to me.

I have been looking at your build and must say I really like it and the mudroom build around it.

Good job!

 

[oreo54]

This might help as well. A bit fuzzy but it's a 31x 31 inch PAR map, height???

Treasure trove o data..
https://www.hennings-miniriff.ch/led-module/giesemann/giesemann-vervve-160-180w/

 

[NatD]

Some great responses. Wow. Thanks. I'll do my best to answer.

Do you want full coverage top/bottom or sacrifice some light at the top for more PAR deeper??

Full coverage is more important. I believe that with a shallow tank and 4 units I should have ample PAR. I suppose I can always adjust along the way if that becomes necessary. I think a dark spot in the center would be more distracting than light diminishing along the edges.

Pucks might be 6" don't know..Need puck diameter..

Each puck is 3.25" and there are 2 per unit.

Whats the lens beam angle?

I can't find this. Not even in the owner's manual. The BRSTv review calls it "ultra wide angle" but that's rather unspecific. I could plug one in and measure...

Agreed. This would be trial and error to me.

I have been looking at your build and must say I really like it and the mudroom build around it.

Good job!

Ah thanks so much. It's quite enjoyable. I'm glad my husband went along with building this -- who needs a "breakfast nook" anyway? I do appreciate you following along.

Sounds like I'll be hanging them with my best guess (which is now a lot more educated! Thanks!) and accepting that we may move later.

 

[oreo54]

Since most reef fixtures do 90 degree max down to like 60.. pretty sure "ultra wide" is 120-ish..
A diodes "native" angle is about 150-ish w/ most having rudimentary lenses of 120 or so.

 

[oreo54]

Lets assume its 120 degrees for now.
Your light cone diameter is 20" as represented by the grey circle. This is centered (roughly) around the center diode on the one puck (green dot) to make life easier.
As you raise the light the cone expands. 28" at 8"
To compensate you would move the fixtures in along my should be straight green axis and the green center dot.

AT 8" off the water line this translates:
Roughly 10" apart on the short side.. Almost touching on the long side..CASES not puck centers or anything like it.
somewhat counter intuitive but I think it is correct..

sooo.. basically 18" to 10" apart on the short side to 10" to nothing on the long side of the CASES not the pucks.. @ 6" to 8" above the surface and 120 degree beam angles..
Black rectangles are approx the case size btw..

 

[NatD]

Your love of this hobby really shines through in your answers and the time you take. Really kind and rather impressive. Thank you.

I will absolutely use your advice.

Looks like 8” above the surface is the winner for the 28” light cone from each puck as well.

I hadn’t thought about tangents in probably 20 years