Four Steps To Create Star Trails

You may have seen many images like the one at Left and wondered how they are created, this post from Sayeed Ahmed helps explain the steps needed to produce your own star trail images.

Creating star trail images is a fun technique that can deliver a wide range of results depending on location, foreground objects and number of visible stars. While the technique can be relatively simple, proper setup and then proper post-processing are essential. To get started, let’s look at the equipment and tools needed for a normal star trail image:

• Digital Camera, with or without Bulb mode
• Tripod
• Remote shutter release with timer (optional, but it helps)
• Open view of the sky
• A lack of city lights
• Image stacking software
• Patience and warm clothes if you don’t live in the Tropics

Any camera will work for creating images while it should be noted cameras with exposure length control (shutter priority, manual or bulb modes) work best. The remote shutter release unit is best used to reduce camera shake from pressing the shutter release button as it is used off camera (some are even cordless). If the remote has a timer function it is golden for use with this type of photography. A good timer will allow for setting of the shutter speed, number of shots and interval between shots. This is the best unattended setup if you wish to wait some place warm while your camera takes care of the pictures. Image stacking software allows for the overlay of multiple images while combining the details.

the most important thing required for these kind of photography is

1. Location

Finding a location away from city lights is an important consideration. As the stacking software will combine light areas of the picture, it’s best to have as dark of a sky as possible.

Once a good location is established check the foreground for interesting subject matter. A shot of just the sky, while cool for a few shots, looses its luster without an Earthbound object to anchor the action. Mountains, trees, mesas, even people or buildings can be used to add some interest to the shot. Make sure your tripod is set on firm ground and not in a location it’ll be bumped or walked in front of.

If you wish to get the circle effect in the photo up top, just point your camera toward the North Star or the Southern Cross depending on your hemisphere.

2. Setting Up

First, picking a day is key. You need a dark, ideally haze-less night, and as clear of sky as possible. Low clouds can be OK if you are shooting wide enough (clouds block stars). An occasional quickly moving cloud won’t affect the composite much either.

Once you have an ideal day, make sure you have plenty of time to get to your location, as I found I’d be going to each location around rush hour. I aim to be setup just before sunset, and my setup includes a tripod, a remote release/intervalometer, and an external battery pack (I use a Goal Zero Sherpa 100). The power pack is important because, especially on a cold night, you’ll be shooting longer than your battery lasts, and swapping batteries can bump the camera and cause a gap in the star trails. (It’s also possible to start shooting in the middle of the night and finish around blue hour, but I found it harder to get precise focus during the dark night and harder to wake up at 2am than staying up late.

3. Shooting

This is where the patience and warm clothes come in. And a remote shutter release if you have one. As the Earth is always moving and those stars keep walking across the sky, you’ll want to keep your shutter releases as close to the end of the last shot as possible. Large breaks will cause blank spots in the trails. This effect can actually be used to your advantage if you become real creative, just make sure it’s intentional. Keep shooting until you have as many images as you desire. As a point of reference, the image at the top of this post is a combination of shots over the course of 57 minutes.

If you have an item in the foreground, there are light painting techniques that can be used to highlight them. Only one frame is needed because of the stacking method. For more on painting with light. A lot of fun can be had adding effects to the foreground.

4. Post-Processing(Stacking)

At my computer, I start with a test star stack and do a rough composite onto the base exposure to make sure the shoot worked and the shot has potential. This step is always the most nerve wracking because it’s where you discover problems.

Even when everything works, it can be demoralizing as you see just how much air traffic is in the sky, such as in this composite from Battery Spencer.

The premise here is the program will take your batch of photos and then add them all together to render the final image. Anything reflecting light in all images in the batch will show as especially bright in the final image. Individual starts, when moving across black sky, will combine to create the lines that are so captivating. You may also average all the images of just use the brightest pixel from the batch to create an image. Each pass creates a different view of the same batch of photos, so experiment (have I mentioned that before?  Image Stacker will produce a jpg, bmp or tif file in the location of your choice. Those proficient in Photoshop can also stack images, but the technique is a best left for another post.

And that’s it! It really can be that simple and most importantly it’s usually a lot of fun. Ok, there can be some frustrations as well…..planes flying across the field of view, people shining flashlights toward the camera wondering what you’re doing, small animals bumping the tripod unbeknownst to you. But the results are worth the effort so give it a try and post a link here with your successes!