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5.7 Calibration Spectra

To reduce data taken with this instrument, the following are required:

  1. Bias (zero) frames to determine the structure. The average or median of these frames will be subtracted from all other frames (darks, flats, and object frames).
  2. Darks for long exposures. Multiple darks are essential to improve statistics and to be able to filter out radiation events.
  3. Flat fields: dome flats are preferred over the internal quartz lamp for true long slit work because the dome flat field illuminates the slit much more evenly than does the quartz. However, the present dome spot is dead in the region and the internal quartz lamp is recommended for any work below 4000Å. Internal quartz flats are satisfactory for stellar observations where only a short section of the central slit is used. For long slit work, twilight sky frames are recommended.
  4. Comparison source (HeNeAr) for wavelength calibration.
  5. Standard stars for absolute flux calibration. Stars in the IRS list have data available at more wavelength points than do those in the IIDS list. The work of Massey, Strobel, Barnes, and Anderson Ap.J., 328 ,315,1988) offers improved wavelength spacing, photometric accuracy, and a few new fainter stars than older lists. The following standard stars have flux data longward of 8000 Angstroms and are listed as they appear in the IRAF database onedstds$redcal.

The stars with extended wavelength coverage are noted in Table 5. ** denotes extension to 1 and * denotes extension to 9000Å.

       40erib*      g9937**      hd19445**    13633**      lds749b**

       bd174708**   gd140**      hd84937**    1151234b**   ross627**

       bd262606**   gd190        he3          l74546a**    ross640**

       feige24*     grw705824    hz29         l93080*      sa29130**

       g191b2b**    grw708247*   hz43**       l97030*      wolf1346**

       g4718*       grw738031*   hz44**       lds235b      wolf485a*

        Table 5: Flux Calibration Standard Stars



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Next: Flat Fielding - Dome Spot or Internal Quartz Lamp?
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kessel@noao.edu
Wed Aug 2 13:05:25 MST 1995