The Study of the YFOSC Long-Slit Spectrograph

The YFOSC (Yunnan Faint-Object Spectrograph and Camera) is a powerful instrument for astronomical research which can quickly switch its working mode from the photometric to the spectrophotometric. A main spectroscopic mode is using a long slit with a low-resolution Grism (a combination of grating and prism) to observe point sources or extended objects. This paper first describes the system response function and the wavelength coverage of each grism. We then describe the calibration of the wavelengths of three lamps for observation. We also give the relation between exposure time and object magnitude for practical reference. In the past year we carried out many observations with the YFOSC and obtained some useful data for objects such as supernovae, QSOs, and normal galaxies. We have also used long-slit modes to scan some extended objects such as nearby galaxies to find their velocity fields. We finally present a spectrum from a supernova as an example of application of this instrument.