Record the motion of NLCs

Capture the movement, structure and colours of summer's night-shining clouds

- Pete Lawrence

The lack of truly dark skies is an issue for the UK at this time of year. Some compensation is the chance to see noctilucent cloud (NLC) displays, and this month we'll look at how to photograph them to capture their structural movement.

NLCs are high-altitude ice-sheet clouds able to reflect sunlight despite the Sun being below the horizon from ground level. They are typically seen 90-120 minutes after sunset, low above the northwest horizon or a similar time before sunrise, low above the northeast horizon. Extensive displays may last all night, tracking from the northwest, through the north and ending in the northeast.

There are many interesting things about NLC displays, including their brightness, colour and different types of structure. This can all be seen visually, but recording displays with a camera allows you to create timelapse movies that show how NLCs develop over time and how their structures move.

This isn't particularly complicated to do and the results can be quite stunning, revealing aspects of NLCs that you may not have realised were there.

Let's consider the basics of an NLC capture setup, starting with the obvious: a camera that is capable of capturing them. Adjustment to the camera settings should allow a fair bit of control to get the best image possible. You should also bear in mind that NLCs appear against a twilight sky. This is one of the most challenging backgrounds in astronomy, as light levels are constantly changing, meaning you need to stay sharp to avoid under- or overexposure.

A wide lens is ideal for capturing panoramic views of a display, but will also reduce the size of cloud structures and the apparent speed of any movement.