Adjustable halide mounts

[zeltar]

I am getting ready to finish my canopy for my 120. I want to create some king of lift/lower system for the lamps (250W Reef Optix)x2. I envision some kind of dowel (broomstick thickness) with some galvanized cable to some pulleys. This would allow for easy height adjustment for acclimating to new bulbs etc.

Has any one else thought of something like this? Is there something on the market for sale that would accomplish the same thing?

Comment and questions recommended.

Thanks.
--Eric

 

[DonW]

How much movement do you want? Are they going to be in a canopy or hanging from the ceiling?

Don

 

[zeltar]

My canopy is 15" tall and I really havent thought about the total movement but probably 5-6" inches would be enough maybe more just because.
Got an ider for me??????

 

[DonW]

I would simply mount the lights on a rod. Have both ends of the rod in a groove. put a escentric disc on each end of the rod. When the rod is turned the lights move up and down.

Don

 

[DonW]

here is a pic

 

[zeltar]

I can see clearly now, the rain has gone......

That is a great idea, much simpler to build and use. My brain had waaaay too many parts involved. I'll see what I can come up with and take some pics.

Thanks for your "vision".

 

[NaH2O]

Eric - you might want to check out Maxx/Nick's thread. He used a pulley system for his lights.
Project 58!! - page 1...you can see the design in post #2 that he based his off of.

Project 58 - page 11 - this is the start of the pics showing his dowel system going together.

Hope it helps!

 

[zeltar]

Great thread, thanks Nikki. That is kind of what I thought I wanted, but dont have that kind of room in my canopy. But I can take some of that info and make it work for my system. That is the beauty of this site, copy/steal/borrow and ignite imagination.

Thanks for all of the input.

 

[DonW]

Just to complicate things a little. You could have a knob on the outside to move it up and down.

Don

 

[dnjan]

This would allow for easy height adjustment for acclimating to new bulbs etc.

As long as you have decent reflectors, moving your MH's up or down inches (or even feet) will have almost no effect on the light intensity in the water.
If you are worried about new bulbs being too bright, use a couple of thicknesses of plastic window screen just above the tank.

 

[DonW]

As long as you have decent reflectors, moving your MH's up or down inches (or even feet) will have almost no effect on the light intensity in the water.
If you are worried about new bulbs being too bright, use a couple of thicknesses of plastic window screen just above the tank.

I may be missing something, but while reading Sanjay's reflector test the difference between 6,9 and 12" was huge.
Can you explain?

Don

 

[zeltar]

Good point you have there DNJAN. I have brand spanking new Reef Optix III 250WDE units. So as I always to I am over-engineering this.... With that now out of the equation, what is the recommended (if any) hieght off the water? My tank is 24" deep x 24" high x 48" long.

Thanks for putting the hamster in my brain on vacation.

 

[NaH2O]

I may be missing something, but while reading Sanjay's reflector test the difference between 6,9 and 12" was huge.
Can you explain?

Don

I agree, Don. I believe this might help - Inverse Square Law? Here is a link to Sanjay's article showing the percent loss of PPFD at different heights: Analyzing Reflectors: Part III

 

[DonW]

I agree, Don. I believe this might help - Inverse Square Law? Here is a link to Sanjay's article showing the percent loss of PPFD at different heights: Analyzing Reflectors: Part III

If I'm understanding that correctly? The Reef Optics reflector will have a 24% reduction over a 2x2 area. Right???

Don

 

[zeltar]

Wake up hamster, vacation is over........
Ah man, just when I thought it was outta the woods you guys bring up that MATH thing. Now I'm hosed for sure. So there is a benefit/concerne for height adjustment for your MH's. I havent read the above links yet, as I am at ahem, "work" but will give them a look later tonight.

 

[NaH2O]

If I'm understanding that correctly? The Reef Optics reflector will have a 24% reduction over a 2x2 area. Right???

Don

That's the way I read it, Don. If you look at the chart above, you can also see the maximum PPFD at the different heights.

 

[dnjan]

The inverse square law applies to a point light source in a vaccum, with no reflector.

With a proper reflector, the light that bounces off the reflector hits the water surface at close to a 90-degree angle. This is important, as the percentage of light that actually penetrates the water surface (reflectance versus refractance) depends on the angle of incidence.

So - the light getting into our tanks mostly comes from the reflector, not in a direct line from the bulb (because the direct line from the bulb quickly becomes less than 90-degrees as you move out from directly below the bulb itself.
I believe Sanjay's readings were done in air, correct? So the reflectance/refractance at the air-water interface would have been left out.
I had e-mailed him a while back asking for a clarification, but did not get a response.

 

[mojoreef]

Well you lost me my friend?? lol
Speaking in general terms here. If you have a light that is in a reflector and the reflector sits 3 inches off the surface. The vast majority of the light, from either the reflector or the the bulb is directed towards the water interface.
Now if you raise the reflector say 3 more inches of the water you are going to letting more light out as thier is a greater amount of open area between them, right?? So photon energy is lost, then you add a greater amount of refractance and reflectance due to more water surface area being bombarded by photon, you loose even more.

I tend to follow the loss of energy when raising lights. But maybe I am missing something??


Mike

 

[dnjan]

Mike - if the reflector is a true parabolic reflector, the light from the reflector should be hitting the water surface at 90 degrees to the surface, No matter what the height of the reflector. So, for the reflected light, height makes no difference.

For the direct light, as the angle between the light source and the water surface decreases below 90 degrees, the amount of "lost" light (light that is reflected rather than enteringthe water surface) increases. So, the closer the bulb is to the water surface, less the area of tank that is illuminated by light penetrating the water.

For simplification purposes, lets assume that very little light penetrates when the angle is less than 45 degrees. So, only half the light coming from the front (bottom) side of the bulb does any good. The rest, even though it hits the water surface, is reflected away (this is a simplification, but the general idea holds) becausethe angle the light hits the water is too shallow. But, almost all of the light from the back (top) of the bulb hits the reflector and is reflected down at 90 degrees to the water surface. (note - therein lies the advantage of the DE bulbs - the bulb body itself blocks less of the reflected light than a SE bulb).

Therefore, most of the light actually enterring the tank comes from the reflector, and with a proper reflector, height above water has minimal effect.

Another consideration - With the bulb at 3" above the water (your previous example, Mike), you are only illuminating a 6x6 square by direct light. Raise the light an additional three inches, and you are illuminating a 12x12 square. Yes, the illumination on that 12x12 square from direct light is less intense than the light on the 6x6 square from direct light, but who wants to have 'spotlight" areas. Plus, there is still more light enterring the tank from the reflector.

Most reflectora are somewhat of a compromise between reflector size and area covered. A true parabolic reflector would only light (by reflected light) the area directly under the reflector. Most of the better reflectors allow for a slight amount of spread from the reflected light in order to illuminate a larger area without having to have such a large reflector. But they still keep the light at close to 90 degrees for maximum penetration.

 

[mojoreef]

For the direct light, as the angle between the light source and the water surface decreases below 90 degrees, the amount of "lost" light (light that is reflected rather than enteringthe water surface) increases. So, the closer the bulb is to the water surface, less the area of tank that is illuminated by light penetrating the water.

Sure but you are still loosing the overall energy being put out by that light no?? If you lift the light to cover a broader area of the tank you are in effect loosing photons (light energy) as a sacrifice for cover more of an area??

(note - therein lies the advantage of the DE bulbs - the bulb body itself blocks less of the reflected light than a SE bulb).

Thiers not a lot of difference between a de and a se when it comes to things light doesnt penetrate no?

Therefore, most of the light actually enterring the tank comes from the reflector, and with a proper reflector, height above water has minimal effect.

I agree with the fact that most of the light comes from the reflector, but I still cant get around that you loose more light energy by raising it. If you look at the surface of the water in our tank they are rippled, even light penetrating at a 90 degree angle still has a small chane at making past the water surface into the tank at the same 90 degrees. Now if you raise the reflector you are subjecting that same amount of light energy to more surface area and thus more area for it to be reflected away or on a longer path to its destination.

Another consideration - With the bulb at 3" above the water (your previous example, Mike), you are only illuminating a 6x6 square by direct light. Raise the light an additional three inches, and you are illuminating a 12x12 square. Yes, the illumination on that 12x12 square from direct light is less intense than the light on the 6x6 square from direct light, but who wants to have 'spotlight" areas. Plus, there is still more light enterring the tank from the reflector.

I dont think so? I cant see how you will have more light energy entering the tank by raising it. If you raise it as you say and the result as you say is less intencity then you have lost some or reduced the intencity. I think that you will cover more area of the tank, but that would be with less total energy.

Now we are using 3 inches as a benchmark here but that is alot closer then most of us do. In the question of Zeltar he want to be able to adjust the height of the lighting in order to adjust the intencity of the light penetrating the tank, I think its viable, or am I still not getting something, lol

Mike