dawn and dusk

[realhiphop]

can someone simply explain how to simulate dawn and dusk with lights? what exactly does this mean? do you need 2 independent light switches? and how do you do this with automatic timers and specific light bulbs?

[Satchmo]

It simply involves turning your actinics on 1/2hr- 1 hr before your daylight bulbs go on. Then at night, your actinics stay on for 1/2hr - 1hr after the daylight goes off. There may be a ballast I don't know about with independent bulb controls, but I know with the kit I have (ahsupply), you would need 2 separate ballasts and two timers.

 

It's a really neat effect, but from people I've talked to, dawn/dusk simulation is more for the benefit of the hobbyist rather than the corals. All my lights come on at once, and I've noticed no ill effects or "shock" to my corals.

[anthony812]

i have the 2 switch and 2 plugs lighting system and all you need is 2 timers to set 1 hr longer before and after the daylight comes on...but i can just turn on both lights at the same time..the corals don't really mind..

[Sahin]

Yup, you just get your blue/actinic lights to come on a short while before the main lights come on in the morning, and to go off a short while after the main lights go off in the evening.

 

My actinics have a seperate socket and thus controlled by a timer seperately from the main lights which are also on a timer.

[NaNO ReeFiN]

I don't have the option of actinic lights going on before and after my daytime bulbs so what I do is I open up my hood about 8 inches away from the tank when I turn on the lights and after about 30 minutes, I close my hood so that the lights are about 2 inches away from my tank. This is my version of the dusk/dawn effect... Same thing at night as well.

[MKramer]

I'm curious.... why does everyone suggest that the actinic come on before and go off after the daylight?

 

In nature, the low-spectrum stuff will hit first, then the high-spectrum as the sun climbs higher in the sky. A reef's exposure to actinic radiation wouldn't reach significant levels until hours after sunrise.

 

I'm not saying the method recommended here is wrong, I'm jsut curious why people do it that way. I realize that the actinic lighting in most reef aquariums doesn't even begin to rival the energy created by natural sunlight, so maybe it's done just to give the photosynthesizing plants/animals more time to feed.

 

If anyone has a justification, I'd love to hear it.

[Sahin]

For me, it has to do with the "amount" of light...rather than antyhing else.

 

On my setup, Actinic consists of one tube, whereas for the main lights there are two tubes, which give a lot more light (brightness)...perhaps the "more light" is just our own perception...but thats how it goes.

 

On other setups, eg those with MH halides eg they have 250W of light output, and they supplent this with say 30W actinic...now they'de follow the same idea that the halides give significantly more light (brightness) than the actinics...you get the idea etc etc.

 

Well, this is what I think.

Not sure if others follow the same idea.

[realhiphop]

what exactly is a ballast? and how many ballasts do I need to create the proper dawn dusk effect with timers if I get a 2x55 watt pc light

[Satchmo]

That's an interesting point, and it lends to the notion that dusk/dawn simulation is for the benefit of the aquarist, not the inhabitants. I suppose because the actinics give off a lower, "cooler" looking light, it mimicks (to the human eye anyway) the ambient light of dusk and dawn. Whether or not the corals even care is up for debate. Like I said, my lights come on all at once in all their brilliant glory, and my corals don't seem to mind a bit.

[Satchmo]

The ballast is what runs your lights. I'm far from an electrician, so if you're looking for a better definition, you'll have to wait. But basically, the ballast is plugged into the wall, and the bulbs are connected to the ballast.

 

If you're getting your lights from ahsupply, you'd have to order two separate 55W kits. With the 2x55W kit, you will be unable to operate the bulbs independent of one another. It may be a different story with other manufacterer's kits, but ahsupply is the only one I'm familiar with.

 

Two single kits will, of course, cost more that one double, so you'll have to decide if dawn/dusk is worth the extra money. For me, it wasn't. Good luck.

[MKramer]

A ballast is a special type of power source, required for fluorescent lighting. Basically, what it does is keep the current flow constant. It's not required in traditional lights, because the resistance of the wire strand in a light bulb barely changes. But fluorescents work by electrifying gases, whose resistance can vary considerably. Without a ballast, a flourescent wouldn't be able to keep itself lit very long.

 

It is entirely possible to drive more than one bulb off of a single ballast. But power switches control only the ballast. So all those bulbs will turn on and off at the same time.

 

If you want to have bulbs that can be turned on and off individually, each one will need its own ballast.

 

For example, I have two 32W SmartLights on my 10gal, each off its own ballast. Each ballast has its own powercord (and switch), so each can be controlled individually. Essentially, each ballast is plugged into its own timer. The timer for the bulb in the back of the canopy is set to turn on at 7am and off at 7pm. The timer for the bulb in the front of the canopy is set for 8am and 6pm. This would be to simulate dawn and dusk conditions.

 

If both of my bulbs were only on one ballast, I coudl only use one time (because there's only one powercord), and my corals and fish would have to deal with going from very dark to 64W of light, which they probably wouldn't enjoy.

 

Matthew

[realhiphop]

PSL has a PC light with 2 independent light switches, and says 2 cords? what does this mean?

[Satchmo]

I'd contact them to make sure, but it sounds like you'd be able to hook each bulb up to a separate timer... which is what you want.

[MKramer]

I do think there is some benefit to a gradual turn-on of lights, especially in strongly-lit reefs. Creatures of the sea are not generally adapted to cope with sudden light-level changes. It is actually quite easy to temporarily, or even permanently blind a fish by turning on all of your reef lighting when a room is completely dark (and has been for hours).

 

Granted, for msot of us, the aquariums are in rooms that will have moderate natural light levels at the time the tank lights go on, so this probably isn't as much of a concern. But I figure with the rather high amount of light we generate in our reef tanks, I'd rather be safe than sorry.