DFOSC at the Danish 1.54m telescope

DFOSC is similar in concept to the EFOSC1 and EFOSC2 instruments. DFOSC will be offered with the ESO CCD #17 Thompson chip as default. Here the pixels corresponds to 051, and the field is 87 x 87. It is hoped that a Ford chip eventually will become available. Here the pixels will correspond to 040 and the field will be 137 x 137.

The instrument efficiency is intermediate between the efficiency of EFOSC1 and EFOSC2 - thus count rate numbers given for the EFOSC instruments can be used if scaled appropriately. The efficiency of the grisms offered with DFOSC is similar to those of the EFOSC instruments.

The table below summarizes the properties for the grisms available for DFOSC.

 
Table: Wavelength coverage and resolution of the grisms

The echelle grism #9 covers the region from 3350Å to 9400Å in the orders from 22 to 7 - this grism is similar to the EFOSC1 echelle grism. Continuous spectral coverage is obtained until 8800Å with the Thompson chip. The echelle grism #13 covers: 3140Å - 3500Å (5. order); 3800-4300 Å (4. order); 4950 - 5560 Å (3. order); and 7260Å - 8280Å (2. order) with the Thompson chip. The efficiency of this grism is slightly better than grism #9. The 3rd order from grism #13 can be isolated using an interference filter (top transmission 80%) - thus long slit spectroscopy can be made in this order.

Grisms 10, 11, and 12 are recommended as cross dispersers, however, grisms 3, 4, 5, 6, and 7 can also be used as cross dispersers.

Slits available are: 08, 10, 15, 20, 25, 5, and 10. A maximum length of 8 can be used.

Standard ESO 60 mm diameter filters can be used in the filter wheel.

DFOSC is well tested and very reliable. The interface to the ESO La Silla environment - CCD and MIDAS - is, however, of preliminary nature.

Further information may be obtained from Per Kjærgaard Rasmussen (per@astro.ku.dk) or Michael Andersen (mia@astro.ku.dk). A preliminary users manual including detailed information on the grisms is available via anonymous ftp from mira.astro.ku.dk - it is located in the directory pub/dfosc.

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