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4.5 Fringes

As with most thinned chips, interference fringes are evident in the red. The fringes have peak-to-peak amplitudes of 5% at 8000Å and 16% at 9000Å. The fringe spacing is about 50Å at 9000. Internal projection flats (quartz) do a reasonable job of removing these fringes IF TAKEN AT THE POSITION OF THE OBJECT so as to minimize wavelength shift due to flexure. Figure 9 shows fringes from a setup with Grating 58.