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5. Spectral Resolution


The SBIG documentation quotes a resolution of 8 Angstroms for our spectrograph in low-dispersion mode. We can test this by measuring the width of unresolved emission lines in actual spectra. As an initial test, I measured the width of the 5460 Angstrom line from one of the zenith pointings from 15 July 2008. I extracted a single row (row 125) from the spectrum and measured the full width at half-maximum (FWHM) of the line to be ~10 Angstroms. Our actual resolution at low-dispersion thus appears to be a bit worse than advertised. At high-dispersion, a similar test produced a FWHM of ~2.5 Angstroms. This, again, is slightly worse than the 2.2 Angstroms quoted in the SBIG documentation.

The spectrograph can be used in four modes with differing spectral resolution. These form a 2x2 array, with grating dispersion and slit-width as the variables. Table 11 shows the resulting spectral resolution for these four modes.

Table 11 - Spectral Resolution
Low-Dispersion High-Dispersion
Wide Slit 40 Angstroms 10 Angstroms
Narrow Slit 10 Angstroms 2.5 Angstroms


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Updated: 2010 July 19 [pbe]