Simple spectrometer for filter test?

[Alaun]

Reading the red filter leakage thread I can propose a simple test:

 

First the equipment: UVIR camera, a lens, and a filter holeder plus some special foil with 1000 lines per mm (from an astroshop)

 

The foil is placed in the filter holder and that is attached to the lens. Spectrometer is ready.

 

 

The second picture shows everything attached to the camera plus a filter to test (I do not show pictures with that filter in front, but without an additional filter, except picture 3.1)

 

 

 

Next picture are several pictures taken from different point light sources ( led, bulb, laser etc & a black paper with a small hole)

 

To the left, there is the original light source to the right is the spectrum produced by the foil

 

 

here is a legend to the pictures (in reverse order)

[Alaun]

And here is a further picture set taken with a blue laser (top) and some fluorescence produced by shining the blue laser on textile (with whitener) (the fourth row is a different light source), the first and third is the pure laser.

 

the artefacts next to the light source are some reflections (due to a very very simple set up)

 

[Andrea B.]

Werner, you rock !!!

I simply must try this.

 

A side question: What is the filter holder you are using? Thanks.

[Alaun]

and one taken with the red laser, a green laser and the P7 flash light ("white light")

 

[Alaun]

The filter holder was proposed by Bjørn (also from an astro shop) the nice thing is you can turn it around so the spectrum comes out horizontal in the picture, I had cut a square piece of the foil and managed to put it into the filter just with some black paper around, not very professional, but effective :)

 

The foil came as letter size sample from AstroMedia in Neustadt (www.astromedia.de) and is called "Durchlicht-Beugungsgitter" and was about 15€ (available with 500 lines and 1000 lines per mm).

 

You should avoid touching the foil with bare fingers, because that will leave prints/grease/dirt on the foil.

 

 

Distance camera light source was about 3 to 4 m, is not critical.

[JCDowdy]

There is a product called a Star Analyser I have been wanting to play with, but I do not know how far it it extends down into the UV.

[Alaun]

If you overexpose, you might get some halos (so dynamic range is limited):

 

[Alaun]

There is a product called a Star Analyser I have been wanting to play with, but I do not know how far it it extends down into the UV.

 

Yes, that is the very same principle.

 

And with photoshop, you can produce similar graphs from the pictures taken. My intention with the lasers was to get some kind of reference points.

 

(not very scientific, that would need something like RawDigger to get the real read outs from the red, green and blue dots)

[Shane]

You can also use the mercury emission lines from an overhead fluorescent light, or mercury street light, to "calibrate" the UV-blue end of the spectrum and sodium lines from a sodium street light for 589.3nm.

[lost cat]

Nice solution! Get your hands on an old CD burner laser at 780nm and a fundamental 1064nm YAG and you've got calibration for the IR too.

[JCDowdy]

There is a product called a Star Analyser I have been wanting to play with, but I do not know how far it it extends down into the UV.

 

I inquired about the Star Analyser and the company provided this information:

 

"The Star Analyser gratings are designed to operate in the visible range, matching the response of a CCD type detector and have a usable efficiency between 350nm and 1000nm, peaking at 500-550nm (the blazed wavelength) and falling off towards the red and violet ends. Outside this range, the efficiency of the gratings will be low and the transparency of the substrate cannot be guaranteed. "

 

This appears consistent with the spectra they show on their website. This of course would not preclude the use of a UV transmitting substitute.

 

Dr Klaus D Schmitt subsequently advised me that he found the Star Analyser transmits insufficient UV for our purposes and provided this transmission plot to be shared on UVP.

 

[Andrea B.]

John and Klaus -- Thank you, gentlemen, for this rundown on the Star Analyzer.

 

I had also been wondering about it.

[Cadmium]

Here is a link that my friend sent me, it is in Russian, but it looks like a similar system:

http://www.rwpbb.ru/test/spectr3.html

[colinbm]

Google is your friend.......https://translate.google.com.au/translate?hl=en&sl=ru&u=http://www.rwpbb.ru/test/spectr3.html&prev=search

[Cadmium]

Indeed Col :-)

[Andrea B.]

Only one mention of UV in there in some early daguerreotype experiment by Draper.

A test with IR remotes does show some capability in the Infrared.

 

Added: Got tired of hacking that Russian as I've forgotten way too much of it and tried the translation link. Suc h translation has certainly come a loooong way since the early days. Not half bad really.

[lost cat]

I wonder if this system can also be used to gain some useful lens transmission data. At the least compare the spectra of an unknown lens to that of a well documented lens like a Kuri, El Nikkor, or Novoflex? Perhaps using a UV only light source?