Geoff, I replaced the DVD wedge with a CD wedge instead.
The design shown has an angle of 60 degrees which is way out compared to my version.
I have an approximate angle which looks more like 30 degrees.
While experimenting with the angle of the CD/DVD, I noticed that the spectra(and the dark lines!) can be blurred and distorted if the angle is not right on!
Also, the viewing hole is about 12mm diameter, not a huge chunky opening like the design indicates.
.......the interior image needs darkness!
Yes, you need to use reflected light : off a white painted building/sheet/paper or similar.
You should be able to see in the reflection on the CD, with your eye right up against the viewing hole(like an eyepeice), the primary spectra to the left, and a fainter secondary spectra to the right.
You might need to move your eye slightly to the left and right to see these.
It's hard to tell whether the focus is at infinity or not. I had my camera set to normal and macro........both worked.......so it seems?
I would imagine that the focus point would be the slit itself.................someone correct me if I'm wrong.
Please show your physicist freind the photos below:
All taken with a DVD as a grating!