How to Shoot and Edit Star Trails

Thomas Chu Photo

Astrophotography is a romantic pursuit. Starlight from hundreds of millions of years ago crosses the vast universe and piles onto the CMOS sensor for dozens of seconds before becoming a gift to humanity.

With even longer exposures, or by stacking star photos taken over a period of time, we can delightfully discover the traces of time. Photographers call these images star trails.

Today Thomas will teach you how to shoot and stack a star-trail photo.

Video tutorial

▶ Watch the video tutorial on Bilibili

HD video:

https://www.bilibili.com/video/av49260086/

Written Outline

1. Because of Earth's rotation, the starry sky is constantly turning. So with a long exposure — for example, a Bulb exposure of 15 minutes or more — you can capture beautiful star trails.

However, photographers generally prefer shooting a continuous series with normal astrophotography settings and stacking them, for the following reasons:

1) It effectively prevents long-exposure noise, and the stacked result doesn't accumulate much noise either.

2) Since normal star settings are used, any single frame can be processed into a beautiful regular night-sky photo, and playing the whole series in sequence makes a time-lapse video.

3) If one or two frames go wrong mid-sequence — sudden light pollution, a blocked lens — the whole set isn't ruined.

2. It's best to avoid the days around the full moon (the 15th of the lunar month) for star trails, because the moonlight is too strong and only a few stars are visible.

It's also best to avoid the days around the new moon (the 1st of the lunar month), because the foreground is very dark and the stars become overly dense.

The rest of the month, when part of the moon is showing, is more suitable for star trails: star density is just right and the foreground is lit by moonlight.

3. For star trails, single-frame settings are generally the same as for star photography: around ISO 3200, f/2.8, 30s under weak moonlight; ISO 800, f/4, 30s is enough under brighter moonlight. In the field, take one test shot first, then adjust settings based on the histogram and the result.

White balance can be set manually between 3500-4000K and kept consistent across the series. For shooting, use a shutter release cable with an interval timer — or simplest of all, set the camera to continuous drive and hold the shutter down with a cable release or app, and the camera will keep shooting.

Generally, 15-60 minutes of continuous shooting yields a nice star trail.

4. Star-trail focusing requires manual focus. Use the camera's rear screen to find a bright star (or a distant light, or the moon), and turn the focus ring until the bright star goes from blurry to a tiny sharp point.

For most lenses, turning the focus ring all the way to the far end is not accurate infinity — the star will still look soft.

Usually you need to come back slightly from the far end to truly reach infinity focus, at which point the star appears as a solid point.

5. In the Northern Hemisphere, aiming north captures concentric circular star trails centered on Polaris. In the Southern Hemisphere, aim south for concentric circles.

Aiming in other directions also produces arc-shaped trails whose center lies outside the frame.

6. For star-trail post-processing, first apply basic Camera Raw exposure adjustments to one frame, then sync them across the entire series.

If there are too many photos or your editing computer has limited memory, export the series as JPEGs from Camera Raw.

7. In Photoshop, load all the images into one file and set the layer blend mode to "Lighten" — beautiful star trails appear.

Star-trail shooting and editing are not complicated, and you can even do it in the city. Give it a try!

You're welcome to submit your star-trail and night-sky photos to the Weibo hashtag #510100公里#.