Can I use a 1.25-inch diffraction grating filter with a C-mount webcam and its lens?
Asked 6/23/2015
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I have a webcam-style camera with a CMOS sensor and C-mount lens. I’d like to use a 1.25-inch astronomy filter, specifically a diffraction grating for simple spectroscopy. Most examples online show the webcam without a lens, with the filter mounted in an adapter and the camera attached to a telescope. I want to use the camera on its own, keeping the lens attached and not using a telescope.
Is there a practical way to place a 1.25-inch diffraction grating in front of a small webcam lens, and will it work well?
Originally by Mehdi. Source · Licensed CC BY-SA 4.0
Mehdi
11y ago
2 Answers
2
As well as the DSLR plus telephoto lens setup shown in your link, I have also used diffraction gratings mounted in front of (modified) web and video cameras as described. http://www.threehillsobservatory.co.uk/astro/spectra_20.htm Because of the very short focal length of the webcam lens however, the length of the spectrum is very short with a 100 line/mm grating. A 300 or 600 l/mm grating would be better for this type of arrangement.
Originally by user48404. Source · Licensed CC BY-SA 4.0
user48404
10y ago
0
Generated from our catalog & community — verify before relying on it.
Yes — a diffraction grating can be used in front of a webcam/video camera lens, not only in a telescope setup. In practice, you mount the grating in front of the lens so the incoming light passes through it before reaching the camera.
The main limitation is the webcam lens itself: these lenses usually have very short focal lengths, so the resulting spectrum will be quite short. That means a low-density grating such as 100 lines/mm may not spread the light enough for useful spectral separation.
For a webcam-with-lens setup, a higher line-density grating such as 300 or 600 lines/mm is likely to work better because it produces greater dispersion and a longer spectrum on the sensor.
So the answer is: yes, it can be done without a telescope, but the short focal length of the webcam lens makes grating choice important.
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AI11y ago
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