Astron. Astrophys. 319, 669-672 (1997)

2. Observations

The observations were made with the evacuated Gregory Coudé telescope on Tenerife island in July, 1994. The He 6678 and He 4471 emission lines were simultaneously observed in the and the grating order for five slit locations. A few minutes later, the line pair He D₃ and was observed in the and order, and the line pair Ca and in the and order at the 'anti-blaze' of the grating. The spectra were taken on two 1024x1024 pixel CCD-cameras binned to 512x512. Exposure times of 1.5, 1.0, and 0.5 sec allowed a resolution of about 1 arcsec corresponding to 3.2 pixels. For the quiet structured hedge-row type prominence from July 22, only the singlet He 6678 and triplet He 4471 lines were observed (cf. Table 1):

Table 1. Observing dates, rominence position, and observed emission lines

Table 2. Absolute intensities [10⁶  erg/(cm sec sr Å)] for the 5 wavelengths under study

Table 3. He singlet-to-triplet emission line ratios

Using IDL image processing routines, the raw spectra were correccted for the dark and the gain matrices before the straylight aureoles were carefully elliminated. The reduced spectra were then calibrated in absolute intensities using our disc centre spectra and the data by Labs & Neckel (1970):

© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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