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Public Lab Research note

Spectrometer slit width thoughts

by warren | July 05, 2014 13:12 05 Jul 13:12 | #10662 | #10662

What I want to do

I'd like to propose a couple changes to the optical slit based on observations. The slit is fantastically precise but for low-light uses I found it hard to get enough light to the sensor. I was thinking that a considerably wider option for slit might really be helpful in the kit. So:

  • wider slit options
  • printing the width next to the slit or at its edge so its easy to tell which it is. Off the right or left edge so it doesn't interfere with readings.

Also I was thinking of how we might use tags to mark some research notes as "proposed improvements" to kits? That could be interesting.


This is a spectrum of sunlight off a cement floor.


This is from two rows of reasonably bright LED lights:



Ta Da! IMG_20140705_213333.jpg

Reply to this comment...

Jeff, Yes, you could double the slit width and double the exposure but you also significantly decrease the resolution. That said, I've noticed that with the Android phone and available apps, that the exposure and camera focus is very difficult to impossible to control. The defocus badly spreads the spectral band (appears less bright) and the lack of exposure control appears to limit the sensitivity. The best I could do was to use macro mode, night mode and ISO 800. Perhaps the new round of GSoC code can resolve some of these prior to slit-width experiments to set options. Cheers, Dave

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Hi warren, we have a problem. We wanted to edit our picture, but it didn't work, because the photo doesn't appear on the screen...

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have you tried switching your camera to "macro" mode? I don't remember having any such low-light problems with the smartphone spec. haven't tried it on the new Nexus 5 like you're using though.

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