The McDonald Observatory Spectrum of Procyon between 4559 and 5780 Å

The optical spectrum of Procyon was observed from McDonald Observatory  on January 30 and 31 1999. We made use of the Harlan J. Smith 2.7m  telescope and the 2dcoudé spectrograph (Tull et al. 1995) at the focal station F1, which provided a resolving power of  200,000. Five different  spectral setups (numbered 1 to 5 in the figure below, where their location in the spectrograph's focal plane is shown) provided almost complete spectral coverage from 4559 to 5780 Å, and  different exposures (up to ten for a single spectral range)  were coadded to reach signal-to-noise ratios in the range 550-2000.



How to read the data
More information about these data
More information about the 2dcoudé spectrograph


The absolute wavelength scale of the atlas has not been corrected for the different systematic shifts that affected the observations (orbital motion, systemic velocity, 'heliocentric' correction, etc.). The relative shifts between different spectral setups were corrected  as described in Allende Prieto et al. (2002).

These cross-dispersed echelle spectra were continuum corrected by fitting a smooth function to the different orders. These removes effectively slow instrumental distortion of the flux, such as the blaze function, and works reasonably well in spectral regions populated by weak lines, but it miserably fails in the proximity of strong lines, whose widths approach or exceed the spectral coverage of a single order. A more adequate treatment for regions around strong lines has been developed and described by Barklem et al. (2002). Careful application of these techniques to these data in the orders  close to HBeta gives much better results in this region. If you worry about the continuum scale in the HBeta region, the following data should, after correcting for a systematic velocity offset,  replace the corresponding segment in the atlas above:

Because the atlas is made from the combination of different orders, systematic errors are likely to happen at the joints. Small discontinuities in the flux will signal such places. If you cannot see some of them, that means the overlapping fluxes from adjacent orders matched very well and  systematic errors are then small.