

I was wondering what conditions should be met to have the "darkest" sky ... Well, obviously there should be no Moon light. The Milky Way and Zodiacal light should not be visible neither , or kept to a minimum, and the image should be taken at a place with no light pollution. If these are correct criteriae, the following picture must be very close to what the "darkest" sky could be. The following image was taken close to new Moon (No Moon light), middle of the night (minimum zodiacal light effect), in the Atacama desert close to Paranal observatory (no light pollution). The chosen place for this picture has the particularity to be located at a latitude which value is close to the declination of the Southern Galactic Pole. The picture was therefore also taken when the galactic pole passes close to zenith, ensuring that there is no Milky Way up in the sky. When all these conditions are met, the very faint Gegenschein becomes visible. Like the zodiacal light, the gegenschein is sunlight reflected by interplanetary dust. Most of this dust is orbiting the Sun in about the ecliptic plane. The faint oval glow of Gegenschein can be seen in Pisces. The picture was taken after Local midnight 10th October 2010, It was a few weeks after Jupiter's opposition, so the bright planet lies just to the west of Gegenschein. The first image of this kind ever taken was made a few years ago here. The "by product" of this image is that the Milky Way plane lies all around the horizon as visible in this 360 degrees panoramic view.

