Question: Question: total beginner problems

viechdokter is asking a question about spectral-workbench: Subscribe to answer questions on this topic

viechdokter asked on March 24, 2016 16:16
672 | 0 answers | #12882

What I want to do or know

I just built up my spectrograph and plugged it into the computer. Problem is, I don't see a real spectrum but only three more or less blue lines. What am I doing wrong? I pointed the device towards diffuse sun light, a candle, a light bulb, and all I am getting are a few blue stripes no yellows, greens or whatever...

Background story


Hi! Can you post what you see in an image, or a link to a spectrum?

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Here is the spectrum:


I wonder if I have put in the DVD-grate the wrong way round or something. I got almost the same three blue lines from a lamp, diffuse sunlight and a candle, so it must be something wrong...

Hmm, can you upload a picture of the inside of your device? That does look wrong, and it's hard to imagine what's causing it. Also, can you upload a picture directly taken through the webcam instead of through the "waterfall" from the live capture interface?

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Hi Warren, first of all thank you for your help. Here are a few images of the setup:




And here is the proof that the camera works:


Hmm, I'm not sure, but it seems like the image is being cut off because the camera is a little too high. See how the black bar covers the area where you might've seen more colors of the spectrum. Can you try lowering the camera so that when the case is open, you see no black?

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I meanwhile tried to "straighten up" things a bit in the setup (although the velcro tape is not very helpful for small adjustments - perhaps one could invent a "cardboard slide in system" for the tray build-up?) and got a continuuos spectrum now, but still the yellows and reds are missing completely. I took this image of another (smaller) IKEA lamp. I also got the impression that the system needs loads of light to work properly. This lets me think that the way of light within my device still is a little bit blocked by something.


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You are right about the cut-off of the picture. Iwill try to work around it.Problem is, the camera already is in the lowest possible position. I could try to lift up the grate a bit but it might effect the angle between grate and camera....

Hi Warren, thanx again for your input. I meanwhile found the problem: the double-sided tape that was supposed to hold the camera in place just stuck to a (loose) quality control sticker on the backside of the camera which eventually came off. The tension of the attached wire pushed the camera off the wooden block holder thus changing the way of the light. I reattached the camera to the block using single sided sticky tape and got this full spectrum now:

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