The three images above show the same HI
channel map, ie the hydrogen gas at one particular velocity, of the spiral
galaxy NGC 3621 using data from the Australia Telescope Compact Array (ATCA).
On the left is the "dirty map", obtained after Fourier-transformation of the
calibrated data; the CLEAN components are shown in the middle, and the
partially CLEANed map is shown on the right. Participants of this week's
Radio Synthesis School in Narrabri will
learn all about interferometric imaging techniques. - The galaxy NGC 3621
is part of the Local Volume HI Survey (LVHIS).