Northern lights on your screen with Aurora

Curtains of green and violet light rippling across a night sky are something most people only see in photographs. Aurora in Screensavers by Zaweba puts a slow, rippling version of the northern lights on your idle screen, above a starry sky and a dark line of hills, drawn by the app's own code.

It is in the classic pack, though its dark sky means it sits comfortably in a dim room in the evening. Four settings let you choose its colours and how lively it is.

The colour choices

Colours has four options. Green with violet is the look most people picture, the bright green of a typical aurora with violet at the edges. Teal and blue is cooler and softer. Rose and violet is warmer and more unusual, closer to the pink displays sometimes seen at lower latitudes. Changing slowly drifts between colours over time, so the sky never stays the same for long.

Changing slowly is a good choice for a screen that is idle for hours, because it keeps the scene from going stale. If you prefer a fixed look that matches the room, choose one of the other three and stick with it.

Brightness, speed and the hills

Brightness runs from 1 to 10. Low brightness gives faint, ghostly curtains that suit a dark bedroom or a late evening. High brightness gives a vivid display that stands out in a lit room. It's worth matching brightness to where the screen is. A very bright aurora on a monitor in a dark room can light up the whole wall.

Speed also runs from 1 to 10, and decides how fast the curtains ripple and move. Real auroras can drift slowly or dance quickly, so there's no wrong answer, but a slow to middling speed gives the most restful result.

The hills can be switched on or off. With them on, a dark line of hills along the bottom gives the sky a horizon and makes the scene feel like a view out of a window. With them off you see only sky and stars, which is more abstract and fills more of the screen with light.

Getting it right in the preview

The manager shows a live preview that follows each setting as you change it. Start with the colours, then set brightness for the room, then speed. Leave the hills on to begin with and see whether you miss them when you turn them off.

After that, press Preview full screen to see it at its real size. A gently rippling sky can look quite different across a whole monitor, and brightness in particular is much easier to judge full size. Moving the mouse more than a little, or pressing any key, closes the preview.

Putting it to work

When you're happy, press Use this screensaver. It is built into your profile without administrator rights, and Windows' Screen Saver Settings opens so you can set the wait time and the password option. Any setting you change later in the manager is used the next time the screensaver starts, without a rebuild.

On a setup with several monitors, an aurora stretched across all of them makes one wide sky with the hills running along the bottom. That is the most impressive way to see it. If you'd rather keep the other screens dark, choose the main monitor only.

Aurora pairs naturally with the night pack. Ticking it with Deep space and Difference clouds in Install several gives a set of dark, starry screensavers, one picked at random each time.

Avoiding a washed-out sky

The most common disappointment is a sky that looks flat. Usually brightness is too high for a dark room or too low for a bright one, so adjust it before anything else. The other is a speed that feels restless; slow it down and the curtains start to look like light rather than animation. If it all goes wrong, Reset to defaults gets you back to where you began.