Image analysis of the observations of the DA240 region with the Miyun radio telescope

Details Image analysis of the observations of the DA240 region with the Miyun radio telescope Image analysis of the observations of the DA240 region with the Miyun radio telescope

Mar 1988

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1988cha%26a..12...70w&link_type=abstract

Chinese Astronomy and Astrophysics, Volume 12, Issue 1, p. 70-78.

Astronomy and Astrophysics

Astrophysics

Scientific paper

In this paper, observations of sky region DA240 with the Miyun Metre-wave Synthesis Radiotelescope (MSRT) at 232 MHz are analysed, using a new method of image processing developed by Wei. Several maps of good quality of the radio source DA240 and its surrounding region are obtained. A number of common problems encountered in metre-wave synthesis systems are solved as follows.
1) Large-scale gradients in the ionosphere give rise to systematic shifts in the apparent one-dimensional positions of sources which in turn result in distortion of the shape of the synthesised beam (see Fig 1b). Instrumental phase errors and ionospheric phase irregularities cause sidelobes and degrade the dynamic range. A new method of one-dimensional image correlation analysis is used to overcome these problems.
2) Low-level interference of long duration and offset of the correlators give rise to circular arcs centred at the north celestial pole. Strong radio interference results in parallel stripes on the map (see Fig. 1a). These rings and stripes are removed by means of a digital filter of artificial fringes.
3) Due to incomplete UV-coverage, there are some radial sidelobes and gratings centred at each source on the maps. A modified CLEAN method is used to remove these sidelobes and gratings.
Comparison between our calibrated maps and those made by other authors at other frequencies indicates that our processing is reliable and effective.

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