|The Spectrum of the Th-Ar Hollow-Cathode Lamp Used with the 2dcoudé Spectrograph|
The Th-Ar hollow-cathode employed is a Westinghouse lamp, Type WL-23418, powered with a 14 mA current. This lamp has been used at McDonald since December 1992. The detector was TK3, a thin 2048 × 2048 Tektronix CCD with 24 µm pixels, which was installed at the R ~ 60,000 focus F3. We used grating E2, a 53.67 gr/mm R2 echelle from Milton Roy Co. We used slit #4, which has a central width of 511 µm (or approx. 1.2 arcsec on the sky). We refer the reader to Tull et al. (1995) for more details about the instrument. Information is also available on-line from the 2dcoudé web page.
The exposures used in this atlas were obtained in three different epochs (December 2000, May 2001, and September 2001), as part of a survey of nearby stars (Lambert, Allende Prieto & Cunha 2001). We scaled and combined 42 individual exposures obtained centering 5112 Å in order 67 in the middle of the CCD (blue setup), and 29 exposures obtained with 5178 Å (in the same order) at the center of TK3 (red setup). The final digital atlas available on the WWW covers the region between 3611.9 and 10596.4 Å.
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