Diffraction Grating Recall!!!
We have just discovered that our manufacturer has provided us
defective diffraction gratings. THESE WILL NOT WORK with
At least 7,000 gratings are affected, maybe more. The manufacturer
cannot tell us when the defective gratings were first incorporated.
If you have received spectrographs and diffraction gratings from us
during 2011, you may be affected.
The defective gratings appear normal and are properly labeled (as 1000 lines/mm Linear Diffraction Grating).
However, the material of which they were produced was bidirectional grating material.
They essentially send a spectrum out in multiple directions, rather than the usual horizontal
ones. These will
not work in the Stanford spectrographs.
How to tell if you have defective gratings
If your students have built their spectrographs, look through a few of them.
If the spectrum appears on top of the spectrograph scale, your gratings are fine.
However, if the spectrum appears in multiple bars on either side of, and close to,
the slit, your gratings are defective.
If you have not built your spectrographs yet, hold one of your gratings horizontal about
2" above a tabletop. Then shine a red laser pointer straight down through it
and look for red spots on your table. If you see 2 or 3 spots in a line, your
grating is fine.
However, if you see a "grid" of spots, 3x3, 4x4, 5x5, etc. then you have
How to get your gratings replaced
The manufacturer will replace all defective gratings. If you have unused gratings,
please return them to us and we will replace them:
Stanford Solar Center
452 Lomita Mall, Room 134
Stanford, CA 94305-4085
If you are unable to return unused gratings, or have
already built your spectroscopes,
then let us know how many you need to have replaced.
To report gratings, please e-mail sol-ctr at sun.stanford.edu.
Make sure you include the number of gratings you need and a shipping address.