Cassegrain f/13.7 focus
Sandiford Cassegrain Echelle Spectrometer (SES)
Users guide for the Sandiford Cass Echelle Guider
Brian Roman is the McDonald Operations staff member responsible for SES.
The Sandiford Cassegrain Echelle spectrograph is capable of R = 60,000 (5 km/s) resolution for two 27 micron pixels using a
slit of one arcsecond. The spectrograph operates over the wavelength range from 3,700 Å to 11,000 Å with high efficiency.
Wavelength coverage is continuous (no gaps between orders) for wavelengths less than 8,500 Å. Cross dispersion is provided by
an LF5 prism in double pass; total spectral coverage in a single exposure is 1,000 Å to 1,500 Å, depending on central
wavelength, greatest in the red and near infrared, and slit lengths up to 6 arcseconds are permitted. The spectrograph operates very
close to true Littrow, and matches the free spectral range of a 23.2 gr/mm, R2 echelle grating to the long dimension of a
Reticon 1200 x 400 CCD (RA2). Autoguiding is available using software optimized for guiding on a slit. A new set of slit apertures was
just installed with significant improvement to the stability and reflectivity of the slit assembly.