Slitless spectrography
The image shows the spectral perspective of Orion.

The emission nebula M42 has a prominent emission in Ha as well as in the green (oxygen) part of the spectrum.

 

 

the orion complex

 

 

The equipment is a SLR camera  fitted with a 85/1,7 objective and in front, a reflexion grating.

the system

 

The main part of the system: The BIG reflexion grating!

reflexion grating