HARPS Diffuse Light Table

Monitoring of the spectrograph diffuse light

HARPS suffers only marginally from scattered diffuse light. This is mostly light coming from unwanted reflections in the lenses or grism of the spectrograph, or even from the CCD surface, despite the antireflection coatings. Obviously this light has a different wavelength dependence than the normal spectrum.

All measurements were done using the saturated (interstellar) NaI D lines (5890 Å and 5896 Å) seen in certain stars (D.E. Welty, L.M.Hobbs, V.Kulkarni, APJ 436:152-175, 1994).

Measurement errors (1 sigma) are below 5%.