The entrance slits of the Ly-
and O VI spectrometers have a
length corresponding to an angular distance of 40 arcmin in the corona.
Ly-
and O VI entrance slit
mechanisms permit a range of entrance slit widths to be selected.
The WLC has a fixed entrance aperture,
corresponding to an instantaneous FOV of 10 
10 arcsec located near
the center of the 40 arcmin FOV of the EUV channels.
All three sections include filter mechanisms, which allow neutral
density filters to be inserted behind the respective entrance slits.
The Ly-
and O VI spectrometer sections use toroidal concave diffraction
gratings in Rowland circle mounts that produce stigmatic images at the
subject wavelengths.
The Ly-
grating has 2400 lines/mm,
and the O VI grating has 3600 lines/mm.
The angles of the gratings are controlled by grating mechanisms.
The null positions place the
H I 1216 
line on the center of the Ly-
detector
and the O VI
1032 
line on the center of the O VI detector. Grating
motions allow the spectral lines to be placed at different locations on
the detectors.
The wavelength ranges for each detector are listed in section 2.4.
The WLC has a filter mechanism which allows a neutral density filter to be inserted just behind the entrance slit. Light from the entrance slit passes through a rotating half-wave plate and a fixed linear polarizer. The waveplate can be rotated into positions 30, 0, or -30 degrees. The selected linear polarization component passes through a color filter and is focused by an achromatic lens onto a visible light detector.