<p>Transmission gratings on their own introduce chromatic aberration.  This is because they change the effective focal length and do so as a function of wavelength.  The chromatic aberration can be eliminated by introducing a prism of the correct dispersion.  Known as a grism, the grating/prism combination provides an unaberrated image at the 0th order in addition to the spectrum, although the spectrum has fairly low resolution. </p>

CC BY-SA 3.0
2015-05-18T21:27:07.550Z
2015-05-19T16:01:46.457Z
2015-05-19T16:01:46.457Z
eshaya
<p>In spectroscopic observations, sometimes you meet grism, sometimes grating. </p>

<p>Both of them could cause light dispersion, but what is the difference?</p>

CC BY-SA 3.0
2015-04-21T10:45:03.733Z
Grism: http://en.wikipedia.org/wiki/Grism
Wayfaring Stranger
CC BY-SA 3.0
2015-04-21T11:04:29.207Z
I know that link.  What is the function of a prism?  A prism itself is enough to disperse light.
questionhang
CC BY-SA 3.0
2015-04-21T11:29:07.287Z
They disperse light with different dispersion functions, allowing astronomers to see different spectral features.
Donald.McLean
<observational-astronomy>
What's the difference between grism and grating?
questionhang
# What's the difference between grism and grating?

(Asked by: username_0 on 2015-04-21)

In spectroscopic observations, sometimes you meet grism, sometimes grating.

Both of them could cause light dispersion, but what is the difference?

**Tags:** observational-astronomy

> **Comments:**
> **username_1**: Grism: http://en.wikipedia.org/wiki/Grism  
> **username_0**: I know that link.  What is the function of a prism?  A prism itself is enough to disperse light.  
> **username_2**: They disperse light with different dispersion functions, allowing astronomers to see different spectral features.  

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## 1 answers

### Answer by username_3 on 2015-05-18. Score: 1

Transmission gratings on their own introduce chromatic aberration. This is because they change the effective focal length and do so as a function of wavelength. The chromatic aberration can be eliminated by introducing a prism of the correct dispersion. Known as a grism, the grating/prism combination provides an unaberrated image at the 0th order in addition to the spectrum, although the spectrum has fairly low resolution.


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