How bright is the moon?

[smlacy]

Hey, how bright is the moon? I know, probably not very bright, but I wanted to get a feel for what sorts of power people were running for their moon lights, and what sorts of lighting periods, and when. That is, if you're using a simple timer to control them. those with controllers need not reply

What about those Cold Cathode "PC Case Lights" that seem to be popular? Are they too bright for a 29g?

My timer has a 7-day cycle, so it would be interesting to come up with a good "plan" for that, how many hours per day, etc. Remember that the moon has both phases (essentially a linear ramp from 0-100% over 14 days, then back down again) And it has the rise/set time as well, which is fairly "random".

Steve

 

[clyde]

a friend of mine who dives, said he was diving a bit before dark, then he came up, WHOA its dark

down there it was pretty bright he said.

 

[smlacy]

You mean your friend thought that it was lighter underwater than on the surface? That would be really weird.

 

[Anonymous]

It is very dangerous to dive during night, and I am sure some divers can attest to it. There is a possibility that during sunset/sunrise, the light cone effect (sun and moon is pretty much always overhead underwater, althought it moves 180 degree across the sky thru out the day) make it appear to be slightly brighter underwater due to the remaining light from the setting sun. The light is not from the moon.

The above is my hypothesis of your friend's observation, and I just want people to keep in mind that it is often easy to mislead and misinterpret observations, and when appling what we heard can be dangerous.

For moonlight, a 5W bulb is sufficient. If someone really want it, I am sure you can find out the intensity of the moon thru out its phase from astronomy website.

Another thing to keep in mind is why you want to have moon light? You may want to read up on the effect of moon simulation on coral, and weight its pros and cons. But if you just want a bulb that you turn on temporarily to see the critter, then you don't have to worry too much other than getting a red bulb.

 

[playfair]

The real answer:
Sunlight ~ 1E+04 CD/M^2
Moonlight ~ 1E-02 CD/M^2

Which means the sun is about 10,000 times brighter than moon
So, if you have a 400 watt lamp over a tank, the moon would have to be .04 watts to be accurate.

In the search, I found this cool little light fall-off math model:
http://illuminations.nctm.org/imath/912 ... mdive.html

 

[smlacy]

Okay, I've done my research now.

Using this webpage: http://aa.usno.navy.mil/data/docs/RS_OneYear.html

I got the sunrise/sunset and moonrise/moonset times for Indonesia (lat/lon: 107 deg W, 6 deg S)

What I found: Indonesia gets a fairly constant 12h30m (750 minutes) of sun per day, year round.

Then, I wrote a small program to parse the output, and figure out what the "visible" moonrise and moonset times are. By "visible" I mean the time that you can actually see the moon after sunset and before sunrise. Here is a sample months worth of output. All times are GMT.

sunrise/set   moonrise/set    minutes of visible moon
13:11  01:09  13:16  00:34  = 0
13:10  01:09  14:03  01:27  = 18
13:10  01:08  14:49  02:19  = 71
13:09  01:08  15:35  03:11  = 123
13:09  01:08  16:22  04:03  = 175
13:08  01:08  17:11  04:56  = 228
13:08  01:08  18:03  05:52  = 284
13:07  01:08  18:59  06:50  = 342
13:07  01:08  19:58  07:51  = 403
13:06  01:07  20:58  08:52  = 465
13:06  01:07  21:58  09:51  = 524
13:05  01:07  22:55  10:47  = 580
13:05  01:07  23:48  11:39  = 632
13:04  01:07  00:00  12:26  = 746
13:04  01:06  00:38  13:10  = 746
13:03  01:06  01:25  13:51  = 698
13:03  01:06  02:10  14:30  = 653
13:02  01:06  02:54  15:09  = 608
13:02  01:06  03:38  15:48  = 564
13:01  01:05  04:22  16:29  = 519
13:01  01:05  05:08  17:11  = 473
13:00  01:05  05:56  17:57  = 424
13:00  01:05  06:45  18:46  = 375
12:59  01:05  07:37  19:37  = 322
12:59  01:04  08:30  20:31  = 269
12:58  01:04  09:23  21:26  = 215
12:58  01:04  10:15  22:20  = 163
12:57  01:04  11:05  23:14  = 112
12:57  01:04  11:53  00:00  = 64
12:56  01:04  12:40  00:07  = 16
12:56  01:03  13:27  00:59  = 0

So, its basically a linear ramp from 0 to 750 minutes (12h30m) over a period of 30 days. Interesting. Because of the differing periods, there will be no correlation between this and the phase of the moon.

BTW, I went out to my local computer store (Fry's) and got a Cold Cathode light and power supply last night for my moon. Total cost: $18.

Now all I need is a timer that runs on "moon time." That would be sweet.

Steve

 

[Anonymous]

Both of you have some really useful data. This thread should marked for archive.

 

[Anonymous]

Both of you have some really useful data. This thread should marked for archive.

well, then i am going to muck it up and point out the painfully obvious fact that the moon creates no light

next question!

 

[ChrisRD]

As you wish DM!

marked for archiving

 

[Idefix]

I read somewhere the moonlight should be below 200 lumen !
Higher then 200 lumen and your symbiosis algae will get no rest (grows best with some rest)

 

[Anonymous]

Don't know about the threshold of photosynethsis, but I am sure Podman does not use reflector in his hood.

 

[liquid]

What about those Cold Cathode "PC Case Lights" that seem to be popular? Are they too bright for a 29g?

Heh, it's what I'm gonna use for my 30 long. The blue's look seriously cool.

Shane

 

[smlacy]

I found some more info on an interesting webpage:

http://www.electro-optical.com/whitepapers/candela.htm

Here's the relevant data, for the archives:

Typical levels of Luminance and Illuminance

Outdoor        Illuminance (lux)     Luminance (cd m-2)
Bright sun     50K - 100K            3K - 6K
Hazy day       25K - 50K             1.5K - 3K
Cloudy bright  10K - 25K             600 - 1.5K
Cloudy dull    2K - 10K              120 - 600
Very dull      100 - 2K              6 - 120
Sunset         1 - 100               0.06 - 6
Full moon      0.01 - 0.1            0.0006 - 0.006
Starlight      0.001 - 0.001         0.000006 - 0.00006

Indoor               Illuminance (lux)     Luminance (cd m-2)
Operating theatre    5K - 10K              300 - 600
Shop windows         1K - 5K               60 - 300
Drawing office       300 - 500             18 - 30
Office               200 - 300             12 - 18
Living rooms         50 - 200              3 - 12
Corridors            50 - 100              3 - 6
Good street light    20                    1.2
Poor street lighting 0.1                   .006

So, from this data, the sun/moon ratio in cd/m^2 (candela per square meter) ranges from 500,000:1 on the high end (a dim sun and a bright moon) to 10,000,000:1 on the low end (a bright sun and a dim moon).

Blue LEDs have a wide variance of brightness. http://digikey.com has them ranging from 0.1 candela to 7.0 candela. So, be very careful what you buy. All LEDs are not made the same.

The bottom of my 29g tank is 30"x13" which is approximately 0.25 square meters. So, using the data from above, I should have between .00150 and .000150 candela over my moon tank. The dimmest LED sold at digikey is .0087 candela.

Obviously, these numbers just don't seem to work out. Its been proven that having a moon light source (typically LEDs or a small 5w "party blub") is beneficial to the tank, but the numbers seem to say that its not so easy to simulate the exact brightness of the moon.

 

[Anonymous]

I am usually skeptical when it come to moon simulation, but if you still can't find the bulb that is dim enough, try to use a piece of gray-colored paper to reflect the light from the bulb and illustrate the tank indirectly... now, that is a better simulation!

 

[jhaag]

Just curious, but I noticed that your fullmoon and new moon and have nothing to do with the actual one since it's based on a 30 day schedule. I don't know about your tank, but I know that every full moon there are tons of snail eggs all over my tank. Obviously this means they notice the gravitational attraction or something else besides just light. I wonder if this matters?

 

[Anonymous]

I am very skeptical about organism able to detect the difference in gravity due to different configuration of sun and moon around Earth. AFAIK, no one had prove it other than mere antedote evidence.

My joint pains get worst during full moon....

 

[liquid]

Wow I just plugged those blue cold cathodes in tonite and they're bright! heh

Shane