Spotlight Product Review: Neptune Systems SKY LED Luminaire

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Neptune Systems has offered sophisticated SCADA (Supervisory Control and Data Acquisition) devices along with analyzers, pumps, ATOs, and others for many years. Although many lighting systems made by others could be controlled by the Apex, only recently has this company offered its own LED luminaire. This article will examine the SKY LED light.

Years ago, LEDs (light-emitting diodes) were regulated to lowly positions, such as on/off indicators on coffee makers. Technological advances have offered diodes capable of producing a rainbow of colors, improved optics and heat management, etc. and are now the choice lighting systems for many aquarium hobbyists.

Specifications These following specifications are current as of the time of this writing. As with any product, the manufacturer reserves the right to modify the product.

Dimensions: Total: 13.75” x 10.25” x 1.5”. The LED array is slightly smaller at 12.875” x 9.25”.

Cord Length: Electrical outlet to rectifier 9power supply): ~3 feet. Rectifier to luminaire: ~15 feet.

Power Consumption (full power): 219 watts.

Cooling: Active cooling by up to 2 fans. I can’t hear them operating in the normal ambient sounds of a lab containing multiple tanks, but they are advertised to generate 33 dB at a distance of one meter when at 100% power.

Definitions of Spectral Bandwidths: Since there is a gradual transition between colors in the spectrum, it is not surprising that definitions of bandwidths vary among reference sources. These are as used for this report: UV-A: 350-399nm; Violet: 400-430nm; Blue: 431-480nm; Green-Blue: 481-490nm; Blue-Green: 491-510nm; Green: 511-530nm; Yellow-Green: 531-570nm; Yellow: 571-580nm; Orange: 581-600nm; Red: 601-700nm. Technically, the red portion of the spectrum should be reported as that radiation of up to about 750nm, but most quantum meters report to only 700nm. Apogee Instruments has released a ‘ePAR’ quantum meter that extends further into the absorption range of P700 found in Photosystem I. But that is a discussion for another time.

Spectral Presets There are 16 spectral quality preset choices with the SKY luminaire. However, it should be noted that there is also a ‘Custom’ option where banks of LEDs, on four channels, can be programmed for both intensity and spectral quality. Thus, the user to has practically unlimited choices. With that said, examinations of the presets are below. Bear in mind these presets are for spectral quality, and light intensity is chosen by the aquarist.

Note: There will a little red radiation in the presets that produce only blue, due to this light exciting the phosphors found those diodes producing ‘white’ light. A spectrometer can see this, but, visually, it is not or only weakly apparent.

AB+ This setting is based on spectrum produced by ATI Blue plus AquaBlue Special T5 lamps in a 4 to 1 ratio, respectively. The preset settings for this mode are 75% for Channel 1 (called Amber); 100% for Channel 2 (called Violet); 100% for Channel 3 (called Royal Blue) and 60% for Channel 4 (called White). See Figures 1 to 3.

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Figure 1.


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Figure 2.


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Figure 3.

PHX14+ This spectral preset is based on light quality produced by a Phoenix 14,000K metal halide lamp. The preset settings for this mode are 30% for Channel 1 (called Amber); 100% for Channel 2 (called Violet); 60% for Channel 3 (called Royal Blue) and 25% for Channel 4 (called White). See Figures 4 to 6.

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Figure 5.


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Figure 6.


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Figure 4.

5,000 Kelvin This spectrum is that of sunlight at 11 am (depending upon a number of variables, of course). The preset settings for this mode are 100% for Channel 1 (called Amber); 8% for Channel 2 (called Violet); 8% for Channel 3 (called Royal Blue) and 100% for Channel 4 (called White). See Figures 7 to 9.


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Figure 7.


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Figure 8.


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Figure 9.

7,000 Kelvin This Kelvin is slightly bluer than sunlight at noon on an overcast day. The preset settings for this mode are 100% for Channel 1 (called Amber); 12% for Channel 2 (called Violet); 15% for Channel 3 (called Royal Blue) and 100% for Channel 4 (called White). See Figures 10 to 12.

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Figure 10.


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Figure 11.


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Figure 12.


10,000 Kelvin
This spectral setting mimics the bluest of sunlight. The preset settings for this mode are 100% for Channel 1 (called Amber); 25% for Channel 2 (called Violet); 40% for Channel 3 (called Royal Blue) and 100% for Channel 4 (called White). See Figures 13 to 15.


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Figure 13.


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Figure 14.


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Figure 15.

12,000 Kelvin This setting mimics the spectral quality of a heavily shaded terrestrial area. The preset settings for this mode are 100% for Channel 1 (called Amber); 35% for Channel 2 (called Violet); 45% for Channel 3 (called Royal Blue) and 100% for Channel 4 (called White). See Figures 16 to 18.

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Figure 16.

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Figure 17.

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Figure 18.

14,000 Kelvin This setting more or less mimics the spectrum of a shallow aquatic environment in ‘clear’, colorless water. The preset settings for this mode are 100% for Channel 1 (called Amber); 50% for Channel 2 (called Violet); 50% for Channel 3 (called Royal Blue) and 100% for Channel 4 (called White). See Figures 19 to 21.

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Figure 19.

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Figure 20.

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Figure 21.
18,000 Kelvin As any snorkeler or SCUBA diver has noted, aquatic environments at depth can be blue in color, due to absorption of warmer wavelengths by water. Coral growths at 40 feet can be luxurious in this blue environment. The preset settings for this mode are 100% for Channel 1 (called Amber); 95% for Channel 2 (called Violet); 95% for Channel 3 (called Royal Blue) and 100% for Channel 4 (called White). See Figures 22 to 24.

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Figure 22.

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Figure 23.

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Figure 24.

20,000K The same comments mentioned for the 18,000K setting apply to this preset as well. The preset settings for this mode are 85% for Channel 1 (called Amber); 100% for Channel 2 (called Violet); 100% for Channel 3 (called Royal Blue) and 85% for Channel 4 (called White). See Figures 25 to 27.

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Figure 25.

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Figure 26.

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Figure 27.

All Blue In this preset, only those LEDs generating UV-A, violet and blue radiation are on. The preset settings for this mode are 0% for Channel 1 (called Amber); 100% for Channel 2 (called Violet); 100% for Channel 3 (called Royal Blue) and 0% for Channel 4 (called White). See Figures 28 to 30.

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Figure 28.

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Figure 29.

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Figure 30.

Deep Blue This preset is different from the ‘All Blue’ setting in that it is mostly blue light that is generated. The preset settings for this mode are 0% for Channel 1 (called Amber); 0% for Channel 2 (called Violet); 100% for Channel 3 (called Royal Blue) and 0% for Channel 4 (called White). See Figures 31 to 33.

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Figure 31.

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Figure 32.

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Figure 33.

Photo Mode The ‘Photo’ mode was not available in the programming of the SKY beta unit I received. It is for those desiring a ‘natural’ light for reef aquarium photography without the use of color-correction filters. The SKY units are now under long-term evaluation making analyses of this function impractical. The preset settings for this mode are 40% for Channel 1 (called Amber); 40% for Channel 2 (called Violet); 40% for Channel 3 (called Royal Blue) and 100% for Channel 4 (called White).

Neptune SKY Mode The Neptune SKY mode resembles the spectrum of the 20K mode, but is slightly less blue. The preset settings for this mode are 75% for Channel 1 (called Amber); 100% for Channel 2 (called Violet); 100% for Channel 3 (called Royal Blue) and 60% for Channel 4 (called White). See Figures 34 to 36.

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Figure 34.

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Figure 35.

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Figure 36.

Coral Growth Mode This mode is the most powerful (intensity wise) of all the presets. The preset settings for this mode are 100% for Channel 1 (called Amber); 100% for Channel 2 (called Violet); 100% for Channel 3 (called Royal Blue) and 100% for Channel 4 (called White). See Figures 37 to 39.

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Figure 37.

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Figure 38.

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Figure 39.
Sunset Mode With this setting, light intensity fades to zero output. The preset settings for this mode are 0% for Channel 1 (called Amber); 0% for Channel 2 (called Violet); 0% for Channel 3 (called Royal Blue) and 0% for Channel 4 (called White).

Dim Setting The preset settings for this mode are 15% for Channel 1 (called Amber); 15% for Channel 2 (called Violet); 15% for Channel 3 (called Royal Blue) and 15% for Channel 4 (called White).

Moonlight There are two options for the spectral composition of moonlight produced by the SKY units – blue and white. Only the blue light is shown below. Light intensity, for obvious reasons, is much less than with ‘daylight’ settings (only a few μmol·m²·sec). See Figures 40 to 42.

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Figure 41.
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Figure 42.

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Figure 43.

Custom Mode The ‘custom’ mode allows the user to select intensity and spectral quality of the four channels. Obviously, this presents a practically unlimited selection.

Light Intensity (400-700nm) Photosynthetically Available Radiation (PAR) Photosynthetically Available Radiation (PAR, and reported as Photosynthetic Photon Flux Density or PPFD in units of micromole per square meter per second) is, as we know (or should know), the bandwidth of light that promotes photosynthesis, and is reported by quantum (or PAR) meters. Most quantum meters measure light in the bandwidth of 400 to 700 nm due to the cutoff points of materials used in the sensors. Recently, meters have been introduced that reports PPFD in the bandwidth 0f ~380 to 720 nm. Figure 44 shows PAR values reported by an Apogee Instruments MQ-510 quantum meter positioned in the air at a standardized distance (9.5”) from the luminaire (measurements were corrected so as to report those seen underwater). Note that the number of light-emitting diodes of a particular color that are actually producing radiation in each setting plays a huge part in the amount of reported PAR.

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Figure 44.
Photosynthetically Usable Radiation (PUR) Photosynthetically Usable Radiation (PUR) is the portion of Photosynthetically Available Radiation (PAR) that is absorbed and utilized by photopigments in the process of photosynthesis. Specifically, absorbability is based on that of phytoplankton at 440nm. There is a complex formula to arrive at PUR. Figure 45 reports that obtained through use of a Seneye meter. It should not be a surprise that, in general, the bluer the radiation field, the higher the PUR value. See Figure 45.

Figure 46 demonstrates the relationship of PAR and PUR.

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Figure 45.

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Figure 46.

Light Distribution As we know, photosynthetic organisms require light. Although the intensity of this light varies among sun and shade Symbiodinium clades/species, results of research and experience has shown us that Photosynthetic Photon Flux Densities (PPFD) of ~150 to ~400 μmol·m²·sec is a reasonable compromise for the maintenance of almost all corals, clams, marine plants and algae, etc. If coral coloration is desired, especially with those corals that have the ability to generate non-fluorescent chromoproteins, light intensity exceeding the photosaturation point is desirable (> ~350 μmol·m²·sec). In addition, many Tridacna calm species show no signs of photoinhibition at high light intensities (1,500 μmol·m²·sec).

Note that these measurements were made in a gray Rubber Maid tub. One SKY luminaire was suspended 9.5” above the water surface, and it at 100% power (such as seen in the Coral Growth Mode, or the Custom Mode with all four channels operating at 100%). See the Discussion section for comments. Realize these measurements are accurate for those conditions of my testing. Your measurements will almost certainly be higher due to internal reflections from the aquarium walls. In addition, positioning of the luminaire (height and others) could have a major impact on light intensities. This applies to any lighting source and is not germane only to the SKY LED luminaire.

I’ve chosen to present graphs of light intensity in two formats. The first (as in Figure 47) is a 3D representation of intensities measured on a flat plane (the ‘mountain’ shaped objects represent light intensity, not depth). The second (as in Figure 48) is a 2D representation of the same measurements, but without as many increments – perhaps the two together give a reasonable estimate of light intensities.

Estimated Light Distribution Just Below Water’s Surface These measurements were taken just below the water surface. No water surface agitation was present and hence no waves were generated that could cause a lensing effect. See Figures 47 and 48.

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Figure 47.

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Figure 48.

Light Distribution at 10 Inches Depth Light intensities at a depth of 10 inches. Again, the water surface was not agitated. See Figures 49 and 50.

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Figure 49.

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Figure 50.

Light Distribution at 18 Inches’ Depth And finally, PPFD (PAR) at a depth of 18 inches. See Figures 51 and 52.

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Figure 51.

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Figure 52.

Color Mixing Early LED models had poor color mixing and suffered from something called the ‘disco ball’ effect. The shimmer or glitter (terms for the technically correct ‘caustic network’) produced by this poor coloring mixing was of distinct bands of differently colored light (depending of course upon the number of differently colored LEDs). The color mixing or blending of light by the SKY does not produce the ‘disco ball’ effect, either to my eye or to a spectrometer. The SKY uses a patented process to blend radiation produced by the various LEDs. See Figure 53.

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Figure 53. The spectral qualities of light produced by the SKY are blended well, and no ‘disco’ effect is apparent to my eye, and not apparent to a spectrometer as well.

Discussion Light systems containing light-emitting diodes are the choice of many hobbyists and for many good reasons. Spectral tuning, dimming of light intensity, lamp longevity, power consumption, heat generation, etc. are all selling points. These comments are not new and have been heard before. Of more importance is the temptation to avoid the ‘horsepower’ race where more wattage is a primary consideration. Many LED luminaires are capable of producing more than enough light, and the SKY light is more than capable in this respect.

When examining the PPFD (PAR) values in the measurements made at various depths, several things should be taken into account. First these measurements were made in a gray plastic tub in order to avoid various factors that disturb the actual light distribution pattern. But this is not the whole story, and the light fields in an aquarium environment will almost certainly be higher. First, internal reflections of light from the viewing panes (whether glass or plastic) of an aquarium can increase the amount of light. Upwelling light should be considered as well. ‘Upwelling’ is defined as that light reflected upwards from internal surfaces, such as sand or aqua scaping materials. White sand will reflect more light upwards than, say, black lava sand. If the aquarium has a colored background pane (such as blue, black, or one covered with calcareous algae), some or most light will be absorbed and not reflected back into the aquarium. All underwater testing was done in a condition of practically non-existent water wave action (which can focus light due to a lensing effect – the shimmer we see when water motion comes into play). Under conditions of strong water surface agitation, the PPFD measurements could double. Lastly, an aquarium lighted by just one light (such as we see in the testing) will not be as highly illuminated as a tank utilized multiple lighting sources. In a nutshell, the ‘at-depth’ measurements should be considered as minimal when compared to real-life aquarium situations.

Long-term evaluation of two SKY luminaires is presently under way. In the conditions of this aquarium, the two lights are running at a maximum of about 30% of full intensity. Coral growth and coloration are good to excellent. As a footnote, these corals will be used in future experiments examining coloration and rates of photosynthesis.

Spectral qualities generated by the SKY are practically unlimited. With all the options available, the color of the light generated should fit the tastes of the most discerning hobbyists. In experiments I did a few years ago (in junction with Fluence Bioengineering), we found that spectral quality generated by those LEDs commonly used in aquarium lighting was secondary to light intensity for zooxanthellae found in the stony corals Porites. This was apparent in testing results, but everyday observations of coral growths in captive conditions seem to confirm that zooxanthellae have the ability to adjust to spectrally distinct light fields in something called ‘chromatic adaptation’. In other words, the types of photopigments found in Symbiodinium species or clades will not change, but their ratios will when they adapt to different colored lighting.

Manufacturer’s Suggested Retail Price (MSRP) The MSRP for the SKY luminaire is $869.95. Included is the SKY LED luminaire, power supply (rectifier) and cord, and Y-cable (This cable allows the same programming to be applied to two SKY luminaires and eliminates the need for adjusting individual lights) plus possible tax and shipping. Four mounting screws are supplied though some sort of optional suspension system will be required unless the light rests upon the top of the aquarium or other support.

Certifications The SKY power supply is UL (Underwriter’s Laboratory) and CE (an abbreviation for a French term ‘European Conformity’) certified.

Control System Control of the SKY can be done through the APEX controller or Bluetooth on a mobile device. Programming is easily done by adding ‘points’ on a linear time scale. Each point can be adjusted for light intensity (up to 100%) and spectral quality (using preconfigured settings or the ‘custom’ function). Downloadable firmware updates are a possibility.

There are several options available for the SKY luminaire, and they are:

SHIMZ SHIMZ is an optional optical diffuser that blends the multi-colored LEDs into a more or less homogenous light field. There are optical portals that allow the light generated by white LEDs to pass without diffusion, resulting in creation of the caustic network (referred to in the hobby as shimmer, glitter, etc.) MSRP is $14.95.

Mounting System Neptune Systems has configured the SKY luminaire to be compatible with many other light mounts. There is also a cable mounting system available at a MSRP of $34.95.

Methods and Materials Spectral qualities of the LEDs were determined by an Ocean Optics USB2000 spectrometer. Corrections were made for ‘electrical dark’ (noise). Measurements were made every 5 milliseconds, and five measurements were averaged. Further smoothing was made by setting boxcar at ‘5’. Data were exported to an Excel worksheet where further analyses was made by a proprietary program. Light intensity (Photosynthetic Photon Flux Density, or PPFD) was determined through use of an Apogee Instruments’ MQ-510 ‘underwater’ quantum meter. Underwater light intensities were measured in a 100-gallon Rubber Maid tub filled with freshwater. The tub is made of a gray plastic which minimizes reflection of light and overcame problems of reflected light influencing light measurements in testing done in glass or acrylic aquaria. PPFD measurements were made every 2 inches on center using three grids (at various depths) made of egg crate material. The luminaire was suspended 9.5 inches above the water’s surface. Photosynthetically Usable Radiation (PUR) and Kelvin were estimated by a Seneye Reef device. Power consumption was reported by the Wattage Report on Neptune Systems APEX.

In Closing Neptune Systems gave me two SKY units for evaluation. After extensive testing, I found advertising claims were accurate. But short-term testing doesn’t always tell the whole story. Instead of archiving these units, I decided to use them on a 120-gallon reef aquarium. Operating at no more than 30% power, these two provide more than enough light. The morning begins with the Coral Growth Mode and transitions to blue light later in the day to showcase coral fluorescence. Figure 54 is of a coral maintained under these lamps for several months. I’ll let it speak for itself.

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Figure 54.
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