(V-I) colour index in NGC 1232

This "(V-I) colour-index image" was produced in the same way as eso9920k. It is based on two other exposures, taken on the same date, through a visual-green filter (V) and a near-infrared-red filter (I), respectively. The exposure time was 3 min for both. The field size and orientation is the same. The round, dark spot at the upper left is an artefact. Dust lanes in the spiral arms absorb more green light and therefore appear redder than their surroundings. In this differential image, they are seen as dark regions. They are exceptionally sharp and particularly strong in the inner part of the galaxy.