Light Measuring Equiptments

[stinky]

This is what I hope to achieve ...

BASIC :
1. I hope to extend the life of my bulbs by measuring its drop in output.
2. I also hope to avoid photo shock to corals when moving from one lighting system to another, or when changing new bulbs.

SECONDARY :
3. It would be nice to know the exact high light and low light spots in my tank to help in coral placements.

I know that I can achieve the above with a par meter ... but it is way beyond my budget.
Can a lux meter fulfill all 3 of my needs??
Is there a PRACTICAL use of a spectrometer in reefing?

Really confused!!

 

[Russellaqua]

IMO there's no practical use of a spectrometer in reefing. The exact spectra emitted by most bulbs is readily available information, sometimes printed on the bulb packaging. Since the average person has what is really a quite shallow tank, and the bulbs tend to be high on the blue end of the spectrum, the attenuation of light with water depth is insignificant with respect to reef keeping. If the light were heavy on the yellow end of the spectrum, and the tank very deep (i.e. several meters deep) it would become more important. Not sure about the par meter, but I'd imagine it would give you a good idea of your tank conditions.

 

[coral88]

IMO there's no practical use of a spectrometer in reefing. The exact spectra emitted by most bulbs is readily available information, sometimes printed on the bulb packaging. Since the average person has what is really a quite shallow tank, and the bulbs tend to be high on the blue end of the spectrum, the attenuation of light with water depth is insignificant with respect to reef keeping. If the light were heavy on the yellow end of the spectrum, and the tank very deep (i.e. several meters deep) it would become more important. Not sure about the par meter, but I'd imagine it would give you a good idea of your tank conditions.

Sorry but you could not be more wrong.

The spectrum and intensity of the bulb changes as the bulb gets older. And water has a very big impact on how much light gets to the coral. I am getting a lux meter In the near future. I’ll post some readings. I am also interested in any cost effective spectrometers anyone knows about.

 

[stinky]

The ONLY use for spectrometer that I can think of is to see when we should change our bulbs. If we track the change in spectrum of a new bulb, it might give us an indication of when we should do the change.

However, I think a lux or par meter would be better at guaging when to change the bulb ... which makes the spectrometer not so useful.

 

[stinky]

I am getting a lux meter In the near future. I’ll post some readings. I am also interested in any cost effective spectrometers anyone knows about.

Could you please recommend a value-for-money lux meter???

I read that spectrometer from Project Star is highly recommended.

http://www.enasco.com/product/SB26055M

 

[coral88]

The spectrometer would help you to see when and if the bulbs spectrum changed and would also let you compare different bulbs or find a bulb with similar a spectrum. I don’t think for the average hobbyist this would be worth the trouble or the money. But for someone like myself who has several tanks and a wide variety of lighting It may be worth the expense.

I don’t know if it’s cost effective. I’m going with a Milwaukee Instruments Smart Lux Light Meter. They are about $80.

 

[Russellaqua]

Sorry but you could not be more wrong.

The spectrum and intensity of the bulb changes as the bulb gets older. And water has a very big impact on how much light gets to the coral. I am getting a lux meter In the near future. I’ll post some readings. I am also interested in any cost effective spectrometers anyone knows about.

I agree spectrum and intensity of a bulb changes with age. This is easily dealt with by regular bulb changes. Generally, a bulb has a working life of no more than 9 months, maybe a year at most. Manufacturers are very open about this, partly because they want to sell you more bulbs. In our very shallow tanks water doesn't attenuate light very much, nothing like real world water depths. There is some attenuation, but it isn't huge. Most reef keepers don't have tanks more than a meter deep.

 

[Russellaqua]

In the figure above from:
http://oceanworld.tamu.edu/resources/ocng_textbook/chapter06/chapter06_10.htm
we'll focus on the left side and the line labelled "I." This line represents the transmittance of light in very pure ocean water (i.e. SPS-type tank conditions). The numbers it gives is the percentage of light transmitted per meter of water depth for each of the covered wavelengths. Given that actinic-type light (blue light) is in the 420-480 nm wavelength range, you can see there is a nearly 100% transmittance of this light at 1 m water depth. Granted, other wavelengths fall off quickly, and the redder light helps spur growth, but the bluer light contributes to the color of the coral. Even near-infrared light is transmitted at over 60% in 1 m of water.

 

[coral88]

Mike Josephs (Dudester) was kind enough to bring over his PAR meter. We took readings at various levels in the tank then notated the results on the reef image, seen below. The larger numbers (in font size) are measurements closer to the front of the tank while the smaller numbers (in font size; not numerical value) were taken towards the back. We did this to show depth and hopefully make it easier to understand the various values in different areas of the tank.


http://www.reefkeeping.com/issues/2008-03/totm/images/parvalues_tb.jpg

It would appear that this guys tank is full of some sort of magic water that filters a lot of light out Just like I said

 

[Russellaqua]

Sounds like a turbidity issue. Particulate matter in the water is absorbing the light. It'd be most similar to lines "II" or "III". Places like the Bahamas follow line "I" more closely. Can't get the numbers though. Reefkeeping doesn't allow linking.

 

[coral88]

So one more reason to get my lux meter It can tell me how clear my water is. I also think it would be nice to see for myself instead of listening to someone’s opinion or what someone trying to sell lights has to say.
I reread this thread and thought I should let you know no offense intended I just disagree. I’m surprised you’re not doing more experiments as you seem to be somewhat scientifically minded. I’m just one of those people that has to see for myself but I do take in what others have to say and appreciate any advice or information offered.

 

[Russellaqua]

The truth is there are tons of variables. Every tank is different, every bulb manufacturer is different. All people can really offer is what their specific tank does, or what should theoretically happen. I would definitely test your own tank though.

 

[stinky]

Thanks guys for the feedback ... so, coming back to the original question, I gather that getting a spectrometer is not so useful, and that with a lux meter, I can achieve the following???

1. Extend the life of my bulbs by measuring its drop in output.
2. Avoid photo shock to corals when moving from one lighting system to another, or when changing new bulbs.
3. Know the exact high light and low light spots in my tank to help in coral placements.

Thanks.

 

[Russellaqua]

Sounds right on with all 3. Just keep in mind that with #3 it is mainly the red end of the spectrum that can be lost by up to 40% per meter of water. This is the light usually associated with growth, but the blue light associated with keeping good color suffers from little attenuation at 1 meter unless the water is turbid. Any "floaties" in the water will absorb some of the light, reducing your overall amount of light per area at any given depth.