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Development of a spectrograph for area spectroscopic observations of faint extended objects in optical spectral region (Ohtani et al., 1994) was completed and the instrument is now in commission at the 188 cm telescope of the Okayama Astrophysical Observatory. With this instrument can be made four different kinds of spectroscopy which are switched to one another by remote operation. The four modes are filter imaging at several narrow (or wide) bands, slit scan in the long-slit spectrograph mode, imaging Fabry-Perot interferometer observation, and integral field spectroscopy (IFS). The first two modes of these are conventional types. Two Fabry-Perot etalons of Queensgate Instruments, resolving power R equals 300 (tunable narrow band filter) and 7000, are available. Prior to development of the spectrograph, characteristics of these etalon were examined in detail by laboratory experiments. Effective finess and nonuniformity were measured. Further, behaviors of drift of transmitting wavelength with variations of ambient temperature was carefully examined. Based on the results of the experiment, temperature of the etalon in the spectrograph at the telescope is stabilized within plus or minus 0.5 degrees Celsius to attain high performance that drift of the transmitting wavelength does not exceed one tenth of the width of the Airy profile during observations. For the IFS mode, the type of the TIGER spectrograph is employed. Our spectrograph has a dual-channel enlarging optics, one channel acquiring a target object and the other an 'uncontaminated' sky field well apart from the target. The microlenses array is shared by the target and the sky. With the 188 cm telescope a 9' X 15' (7 X 11 lenslets corresponding 1'.3 square) target field and a smaller sky field 3'.7 apart are observed simultaneously. Spectra on the CCD partially superpose each other with adjacent spectra because appreciable deviations in the microlenses array format exist from an exact square array. However, energy loss due to truncation of superposed part is not serious. Total quantum efficiency of the system is 2 percent at peak. Some results of astronomical applications for active galaxies are presented. Results of super-wide-field observations with an objective of a short focal length is also demonstrated.
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