written by: A. Jitesh•edited by: Rhonda Callow•updated: 4/30/2013
One of the simplest forms of astrophotography is capturing star trails. From helpful tips and tricks to required equipment and recommended camera settings, this tutorial teaches you how to shoot the most enthralling of star trail photographs.
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This tutorial on shooting star trails covers basic precautions to be taken and preparations to be made. It outlines the technique to be used with cameras having a ‘bulb’ exposure mode (usually the higher end SLRs) as well as cameras without (usually entry level dSLRs and most point-and-shoot digital cameras).
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What are Star Trails?
The universe is comprised of millions of stars, and our earth is only a planet associated with one such star, the sun. Rotation of the earth on its axis gives rise to day and night, making the sun appear to rise and set. We can clearly see the sun go round in a huge arc across the sky, but rarely do we consider that the same holds for the millions of other stars too. The rotation of the earth makes the stars take a circular path around the sky. This ‘movement’ is too slow for our eyes to notice. But given sufficient time, your camera can capture it, which appears as a bright streak across the dark night skies. These ‘star trails’ make for very interesting photographs, as you’d agree from seeing the images on the following page.
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How to Photograph Star Trails
Capturing star trails with your digital camera is not astrophysics!! Though it certainly is what you’d call astrophotography! Terminologies apart, the technique is quite simple, but requires certain efforts as well.
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1. Avoid Light Pollution
Starlight comes from millions of light years away, and is quite faint. A bright light in the vicinity of the camera would cause over-exposure and make the star trails invisible (that’s the reason why you can't see the stars during daytime). The city has its streetlights and lights from other sources, contributing to a lot of ‘light pollution’; hence the first requirement for a good star trail photo is to be as far away from a city as possible. Remember the moon too is quite a good source of light, especially the full moon, which is best avoided. A partial moon would be helpful though, to get the foreground details captured.
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2. Make Sure You Have the Right Camera Equipment
Here is what you need to capture star trails:
Your camera: Yup, don’t forget your main weapon!
Lens: Try to use a wide aperture lens. Light will be scarce and a narrow aperture might mean much longer exposures (and consequently, higher noise). You won't need a superzoom though, a medium range room (around 80mm) will help in composition.
Tripod: If you left this one out, pack off and retire for the night! A tripod is a must.
Power: You'll be taking long exposure and multiple exposures. Capturing star trails can even require 2-3 hours of continuous shooting, in the cold night. Make sure you have a couple of fully charged batteries with you, and keep them warm.
Memory: Take as much of it as possible. You don’t want to run out of space in the middle of the night at a faraway location!
Protection for your camera: Nights are cold and there are chances of dew or condensation. Take along a cover for your camera. A small portable battery powered fan for blowing air on the lens would also help to prevent fogging.
Warm clothes and gloves: It's not just your camera that needs to be protected from the elements!
Flashlight: You’ll need it to find your way around in the dark. Also useful for light graffiti (more on this on page two).
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Now that you know how to prepare for capturing star trails and the camera equipment needed, please continue on to page two, where you will learn tips on ideal camera settings, composition and how to actually capture star trails with your digital camera.
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3. Camera Settings
Though there’s nothing like ‘one-fix-optimal-settings’, these tips will give you a place to start experimenting from.
Aperture: A wide aperture means more light and shorter exposures. The downside is a shallow depth of field. So while you may get the stars in focus, any foreground detail might be blurred. Depending on your composition, you may want to use a slightly wider aperture. Around f/4 or f/5.6 should suit most instances.
ISO: With digital cameras, high ISO settings are often accompanied by high noise. Though cranking up the ISO to 3200 seems tempting, I’d recommend nothing more than 800. If you have the time, you can re-shoot at 1600 and compare the output.
In-camera Noise Reduction: If your camera has this setting, be sure to turn it off. If left on, the camera will process each image before shooting the next one, leading to intermittent lag time.
White Balance: Best is to leave in Auto. But try out Tungsten and compare results.
Other Settings: Enable ‘mirror lockup’ and use the timer or remote shutter release to minimize shake.
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There are basically three styles of star trail photos I’ve seen:
Wide shots having a foreground: These are usually the most spectacular looking images, as the star trails are in context to an appealing foreground. You can experiment depending on your surroundings (a lake, a monument, your tent, etc.) and choose a wide enough focal length to accommodate it. Try to get the Pole Star in frame, as all other stars would be rotating around this one.
Zoom in for an abstract effect: Zooming in and filling the frame with only the star trails gives an artistic effect. The bit about the Pole Star holds true here too.
Light graffiti: A wonderful experiment you can try is using your flashlight as a ‘brush’ to ‘paint’ the foreground. As exposures will be for many minutes, you can slowly cover the entire foreground or draw shapes with your flashlight on the foreground. Try it out, its worth all the effort and gives amazing results. Click here for more tips on light graffiti.
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5. Taking the Shot
Now that we’ve taken care of camera settings, we come to the actual shot.
For cameras that have a ‘Bulb’ shutter speed setting: Set your camera to ‘Bulb’ and set an exposure time of at least 20 minutes. That would give you a small star trail. Check for composition, exposure and foreground. If satisfied, try out longer exposures in the range of 30 minutes to 3 hours to get much longer trails. A point to remember with digital cameras is that longer exposures would result in excessive noise. At a 2-3 hour exposure, the noise can be overpoweringly annoying. The solution is to take multiple photos with smaller exposure times.
Cameras that don't have a ‘Bulb’ setting - most compact digital cameras: All but high-end professional cameras don’t have a ‘Bulb’ setting. For such cameras, and to avoid digital noise accompanying long exposures, follow these tips and techniques:
Set your camera on ‘Continuous Shoot / Burst’ mode with the option to shoot until the memory card is full.
Insert the highest capacity memory card you have (make sure its empty).
Set shutter speed to 30 seconds.
Start shooting! Manually adjust exposure time as required, for between 20 minutes and 3 hours. Make sure your camera (and you) are warm and dry.
So what you’ll end up with is a series of photos captured every 30 seconds - this results in about 240 photos if you shot for 2 hours – now you see why you need a large enough card and lots of power.
Finally you’ll need to create one composite image by stacking all these images one over the other. This is done quite easily in Photoshop.
Open Photoshop. Open the first image, make any contrast or curve tweaks that you’d do as for any other image.
Click Select All > Synchronize, making sure you have ‘Everything’ selected. Click ‘OK'.
Load your pictures in Photoshop. Select each of the images, copy it and paste it over the first image. It appears as a separate layer. Do this for all images.
For each layer except the first one, change the ‘Blending mode’ to ‘Lighten’.
You may ‘Flatten all layers’ to get the final single image.