Astron. Astrophys. 332, 739-747 (1998)

2. Observations

The four fields were taken out of different programs:

1. Cep, a filament in the Cepheus flare most probably at a distance of pc (Kun 1997). This region represents the bright cirrus component, comprising also molecular clouds.
2. HR, a faint filament in the direction of the star HR 6132. It is projected towards the boundary of the Draco nebula, a faint cirrus cloud at a distance of 600 pc (Herbstmeier et al. 1993).
3. M03, a smooth area on the sky selected for studies of potential zodiacal light structures (Ábrahám et al. 1997).
4. NGP, one of the faintest regions near the north galactic pole selected for studies of the extragalactic background emission (Mattila et al. in preparation).

The observations were performed at m with the C100 array ( pixels) and at 170 and m with the C200 array ( pixels) of ISOPHOT. The raster mode of the Astronomical Observation Template (AOT) P22 (Klaas et al. 1994) was used with the filters C_90, C_160 and C_180, respectively. The rasters were performed in the spacecraft () coordinate system which is parallel to the edges of the detector arrays. Observational details are given in Table 1.

Table 1. Observational parameters and analysis results for the ISOPHOT observations of the four cirrus regions. Given are reference wavelength, , information on the raster parameters, field size (also accounting for the pixel size) and exposure time, . The exposure time is the time spent observing one raster position. For non-oversampled reasters (M03_90, M03_180, NGP_180) it corresponds to the measurement time per sky position. For maps oversampled in both dimensions (HR_90, HR_170) the effective measurement time per sky position is (C100) or (C200), respectively. For Cep 90 and Cep 170, which were oversampled in one direction only, the effective measurement time is for a subset of the map points.

© European Southern Observatory (ESO) 1998

Online publication: March 23, 1998
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