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van der Steen, M. Spectrum of moon light. Retrieved June 8, 2024, from https://olino.org/blog/ ... /spectrum-of-moon-light 
Added by: Sarina (2024-06-08 09:43:28)   Last edited by: Sarina (2024-06-08 10:36:31)
Resource type: Web Site
BibTeX citation key: vanderSteen2024
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Categories: Englisch = English
Keywords: Sonne = Sun, Spektrum = Spectrum
Creators: van der Steen
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Meine Sichtweise (Keine vollständige Zusammenfassung des Artikels! Meine Meinung muss nicht mit der Meinung der Autoren übereinstimmen! Bitte lesen Sie auch die Originalarbeit!)     

Hochwertiges Spektrum des Mondlichts, Daten frei zugänglich.


Added by: Sarina  
Notes
When I was looking for a spectrum of moonlight, I could not find it on the internet. As I do a lot of lamp measurements myself (see the category lamp measurements), I decided to measure the moon spectrum myself and put that info available on the internet.

Measurement circumstances

The measurement has been done on 14th of April 2014. It was an evening with few clouds and we had a full moon, well visible. Taking measurements with the spectrometer SpecBos 1211 can then be done in two ways.

1) measurement of the illuminance (in lux). However the expected illuminance is only 1 lux and that results in a very faint spectrum with signals for each wavelength too close to the noise limit to have a nice signal.

2) measurement of luminance (in Cd/mˆ2), and that requires a very well alignment of the measurement device in the direction of the moon, as the sensitivity area of the device in this mode is only two degrees wide.

I mounted the spectrometer on a tripod and kept on aligning and measuring until I had an output with a high signal.

Measurement results

Here the spectrum and derived parameters.

 

 

Anne, I do agree there is energy in the wavelength range between 460-480 nm. However that amount of energy is very little. If I were to measure it in illuminance, then hat would be probably less than 1 lux. I am not sure whether such small amounts of energy would do anything.

About the calibration: the spectrometer I used is calibrated by the supplier every year. He does the calibration on wavelength and also on absolute energy level.

 

Dear Prahallad. I also could not find any moon spectral data on the internet which is why I measured it. Now I had to measure in luminance mode, since in illuminance mode the signal would be too small. I measured 177 cd/m^2 in luminance mode, while the sensitive field of view for the spectrometer was 1.8 degrees (angular diameter). This corresponds to only 7.8E-4 sr. Assuming to measure illuminance, and also assuming only the moon to be a bright object, I would only have measured 0.14 lux (meaning the 177 cd/m^2 = 177 lm/sr/m^2 and as I have measured this over only 7.8E-4 sr, I multiply the 177 x 7.8E-4 and get 0.14 lm/m^2 is 0.14 lux). This is very small and would require a 60 seconds measurement time and 60 seconds dark measurement time. The resulting spectrum would be slightly higher than noise level of the meter.
Now for the sun, I did not measure the sun with the specbos 1211. First, there is a lot of that spectrum to be found on the internet. Second, I cannot measure the sun with the specbos 1211 in luminance mode, since that would directly yield an overexposure. And even in the illuminance mode I would not be able to measure the sun with my specbos 1211 since it can only measure up to 10000 lux and the sun will go much higher than that.
So I am sorry, I do not have the sun’s spectrum for you.

 

 
Dear Guido, if you are going to use a spectrometer (you need it in order to get a full spectrum), then I found that you will need a luminance mode, that way the sensor is much more sensitive and also it is sensitive only in one small field angle. Mine has a angular diameter of 1.8 deg=31 mrad, whereas the moo has an angular diameter of 9 mrad, so it is possible to fit the moon inside the angle of view of my spectrometer. The advantage is high sensitivity and that only in a very small field.
Would you use a spectrometer with cosine sensitive head, you will need to amplification. The telescope will be of help. Only that the telescope should be able to pass all wavelengths where you are interested in. I expect that the glass will absorb the UV.

Dear George. I measured the moon from my address. In the measurement file you can find the time and date. The address coordinates are: latitude: 51.42359906, longitude: 5.40894538. I did not redo the measurement at other moon cycles. It was already hard enough to get a nice measurement with the full moon (I had to point it very precisely as the spectrometer had to be in radiance mode and has then only an acceptance window of 1.8 degrees).
You can use the data, my info is found here: http://www.olino.org/us/contributors/marcel-van-der-steen


  
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