In the following description the telescope is assumed to be parked pointing to the zenith, with the spectrograph mounted. Figure shows schematically the main optical components of the spectrograph. These are:
The following Schott glass colour filters are available: BG28, BG38, UG1, GG385, GG395, GG495, RG630, RG695, RG830. Filters are 25 mm in diameter and 2.5 mm thick.
Two ND filters, 25 mm in diameter and 2 mm thick, are available: ND=1.42, 3.0.
The slit assembly is interchangeable so as to allow the use of a number of slits of fixed width. Two slits are available, of widths 73 m and 110 m (1.0 and 1.5 arcsec respectively). For a typical slit-to-detector reduction factor of about 4.1 (weakly dependent on the angle of incidence on the grating) these slit widths project to approximately 18 m and 27 m at the detector. Access to the slit assembly and optical components is by removing the side-panel. The slit position angle can only be set manually by rotating the instrument turntable with the telescope at zenith park.
Table: Characteristics of gratings for the Richardson Brealey Spectrograph
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Figure: The JKT Richardson-Brealey Spectrograph