Shooting a star trail with a single-lens camera is nothing new. Before the digitalization of a single-lens camera, many photographers used negatives to shoot breathtaking work. After digitalization in recent years, the difficulty of taking photos of star trails have been greatly reduced.

 

Why do stars appear trails?

The stars we see in the night sky are a little bit, why do the photos appear flowing? It is mainly due to the rotation of the earth, which makes it look like the stars are moving very slowly. After the photo has been exposed for a long time (in hours), it will record the trajectory of the stars, and it will also get a photo of the star trail.

Taken at the East Dam of Wanyi Reservoir: F3.2 30 "ISO800 x 80

Taken at the East Dam of Wanyi Reservoir: F3.2 30 “ISO800 x 80

How to Take a Photo of a Star Trail?

It is possible to use digital SLR cameras with long exposures to capture star trails, but after long exposure, there will a lot of noise, which will reduce the quality of the photos. You can use the method of taking multiple photos at the same location and merge them with post-processing. The biggest benefit of these methods:

Low Noise: Assuming that each photo is only exposed for 30 seconds, the merged photo will only have 30 seconds of noise, and the merge will not cause an increase in noise;
Less Light Damage: Merging does not accumulate the luminosity of each photo, the combined photo also has only 30 seconds of light damage; compared with a long exposure, the light damage is lower. It is also because of the light damage in Hong Kong is more serious, the combined method will be more effective.

Photo taken at the East Dam of Wanyi Reservoir: F2.8 25 "ISO400 x 73

The photo was taken at the East Dam of Wanyi Reservoir: F2.8 25 “ISO400 x 73

Things to Note when Using the Merge Method:

  1. When shooting, you need to turn off the camera’s noise reduction function to avoid a lot of time between photos, which will cause the star track to be disconnected after synthesis.
  2. Shoot in Raw format to make the photo more detailed and to adjust color temperature later (this is not necessary)
  3. Turn the lens to manual focus and set it to infinity. If the lens does not have a focusing ruler, you can also use distant lights or moonlight for autofocus. After focusing, switch to manual focus. This distance is infinite. Note that when some lenses are zoomed, the focus distance will change accordingly. For example, Canon 18-55IS Kit Len, if you change the focus, you need to focus again
  4. Connect the tripod, the shutter release, and the hood;
  5. Use Manual Mode (M mode) to set the appropriate aperture shutter ISO and other values:

How to Set the Exposure Value?

If the effect needs to be a star point instead of a star trail, the exposure time needs to be limited, otherwise, the star point will show a trail due to the rotation of the earth:
16mm (full-frame meter), the exposure time preferably is not more than 20 seconds
24mm (full-frame meter), the exposure time preferably is not more than 15 seconds
Due to the limited exposure time, a larger aperture and high ISO shooting are required, for example, F2.8 15 “ISO1600

Photographed in Clearwater Bay: F2.8 15 "ISO1000

Photographed in Clearwater Bay: F2.8 15 “ISO1000

For example, when shooting a star trail, the exposure time does not need to be limited like a star point. You can use a longer shutter speed and the ISO can be lower. For example F3.2 30 “ISO400-800

At the door of the tower: F2.5 30 "ISO250 x 70 shots

At the door of the tower: F2.5 30 “ISO250 x 70 shots

How to make the camera shoot automatically without pressing the shutter button each time?

Just preset the aperture, shutter, and other values, then turn the camera to continuous shooting mode, connect the shutter cable and lock the shutter, and the camera will automatically shoot one by one continuously, even if the shutter cable does not have a timer function. No need to manually press the shutter every time.

How to shoot to make the flow path round?

The star track needs to be circular, and you need to shoot north:

Photo taken at the East Dam of Wanyi Reservoir: F3.2 25 "ISO800 x 140

The photo was taken at the East Dam of Wanyi Reservoir: F3.2 25 “ISO800 x 140

How can I shoot the Galaxy?

If you need to take pictures of the Milky Way, which is south-southeast Hong Kong. You can see the Milky Way Center at different times of the night from April to October each year, and can only reach the outer edge of the Milky Way in winter. So if you want to shoot the galaxy, it is best to do it in summer.

Taken on Po Toi: F2.8 20 "ISO1600

Taken on Po Toi: F2.8 20 “ISO1600

I took a Bunch of Photos, How do I Combine them Into One Star Trail Photo?

You can use the free software “Startrials” (available at http://www.startrails.de/html/software.html ). After downloading and decompressing, double-click Startrials.exe to open the program.

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In “File” → select “open image” → click to merge photos (press Ctrl + A to select all) → then press “Build” → “Startrials” program will automatically merge, so you can get star trail photos, tight Remember to save the merged photos.

My habit is to record the number of photos used in the test exposure and composition at the beginning of the shooting, and then delete them when merging so that the merged photos will be more complete.

I have been in photography for a while, and have been deeply attracted by foreign starry sky photos in recent years. I hope to take beautiful Hoshino photos in Hong Kong, which is considered to be heavily polluted by light.

For more photos of Hong Kong Starry Sky, please visit my website: www.fotop.net/Herman

 

Author: Herman Yeung