Gratings for the Argus Multiple Object Spectrograph

The following gratings can all be used with Argus. Resolutions are shown for 3 pixel images with the Loral 1K x 3K CCD which at the present time is the only CCD available for use with Argus. The projected size of the fibers on this chip is approximately 3 pixels. There is no slit, so this is the limiting resolution.

Gratings 

                              First Order

   Grating #     Lines/mm     Blaze (A)  Resolution (A)  Coverage (A)
                                           (3 pixels)    (3072 pixels)

      250          158         4000           11           Complete
      400          158         8000           11           Complete
      510          300        10000            5.9           6000
      181          316         7500            5.6           5600
      KPGL2        316         4400            5.6           5600
      KPGL3        527         5500            3.4           3300
      420          600         8000            3.0           2900
      KPGL1        632         4200            2.8           2800
      380         1200         8000            1.5           1500
      KPGLF        632         8200            2.8           2800
      450          632        11000            2.8           2800
      KPGLD        790         8500            2.2           2200
      KPGLG        860        11000            2.0           2000
There is also an echelle grating with 316 l/mm, with an effective blaze at 56120 Angstroms. See the echelle mode documentation for information about how to use this grating.

Notes:
  1. These are FIRST order figures. Obviously, not all these gratings are designed to be used in first order. When used in second order, coverage and resolution are half the figure given.
  2. Blaze is in "Littrow", i.e. normal incidence. The effective blaze is about 92% of the Littrow wavelength.
  3. Gratings 400 and 510 are silver coated and thus do not reflect light below about 4000A.
  4. Gratings 510, 420 and 380 are not very efficient in second order.
  5. Grating number 380 produces very bad ghost reflections at some wavelengths.
  6. "Complete" spectral coverage means that the chip is larger than the first order spectrum over the wavelength range to which the chip is sensitive. This does not imply that the chip can be used efficiently over such a large range.
tingerson@noao.edu