A low resolution scanning multiple Fabryhyphen;Perot spectrometer has been built for the observation of very weak extended light sources. The instrument consists of three sets of 7.6 cm diam Fabryhyphen;Perot plates operated in central order; their spacings are in a 3ndash;4ndash;5 ratio and are servo controlled using reference light provided by a single master grating monochromator. The instrument is scanned by varying the wavelength setting on the grating instrument. The resolution of the instrument is variable through the range 0.5ndash;15 A, and its luminosity is equal to that of a 5 cm interference filter with a 65percnt; peak transmittance. The free spectral range is about 125 times the peak halfhyphen;width. Wavelengths in that range are transmitted at a level of 10minus;4or less of the central transmission peak.
展开▼
